After thoroughly updating many of the systems on my boat, here are some observations. The most important observation is financial. I started with a 50 year old classic fiberglass boat. Granted, I got the boat for a song, but it would have been cheaper overall to purchase a boat in better repair.
Dometic has a line of alcohol stoves that I like a lot. It was easy to install since you don't have to deal with a propane locker, lines, solenoids, etc. And, if there's no propane or gasoline aboard, you don't need a sniffer or blower. I do wish they make a slightly larger model, and the oven takes some practice to regulate. Although the oven requires care, I've used it to make bread, cookies and other baked goods.
Living on the boat full-time, two people use about a gallon of fuel every two weeks. In theory, a higher grade of alcohol, one that is as close to pure ethanol as possible, is preferred. I've also used cheaper alcohol from a big box store, and the cheaper alcohol works nearly as well. It might give off more of an odor and it might not last as long, but the difference is small.
Dometic also makes a line of 12 volt self-contained refrigerator/freezer units. These look like coolers and have the compressor and cooling plates built into them. The one I have has been great. I haven't tried to measure the power consumption, but I keep it set at 2°C, and there's been no problem with my power budget. One quirk is that, by default, the compressor will shut down if the voltage drops too low. If you're using this with a starter battery, that makes a lot of sense, but if it's supplied by a bank of house batteries, the unit is too sensitive to a small drop in voltage. There's a way to turn the voltage sensing off so that it will run as long as there's power.
I have a Frigoboat freezer that I am very happy with. The components were sold by Coastal Climate Control. It wasn't difficult to install, but it does take some care, and a mistake would be expensive. Be aware that the compressor does get hot — not too hot to touch, but hot enough to be a factor in where it's placed.
The crucial requirement for an efficient setup is sufficient insulation. Also for efficiency, particularly in warmer waters, I opted for the exterior heat exchanger (i.e., the "hot side" is a plate on the outside of the hull). With close to six inches of insulation, four cubic feet of storage uses very little power. I'm not sure how much power it uses, but I have had no problems staying within my budget with the freezer set for 8°F.
The Lavac head has meant that the days of clogs and finicky pumps is over! Heads I've had in the past would occasionally act up in one way or another, maybe once a month, but there has only been one such instance with the Lavac — a non-boater friend used way (!) too much toilet paper, and the bowl's outlet was plugged. The only downside to the Lavac is that it has the look of a contraption, with a lot of pipes and valves, but that may be how I installed it.
The way the head is set up, when the lid is closed, the bowl is air-tight. Seawater is drawn into the bowl by the suction that results when the contents of the bowl are pumped out. People sometimes complain that the level of the water that's left in the bowl is too much. Lavac provides a small siphon break and — they say — by adjusting the size of the air hole in the siphon break you can change the level of water left in the bowl. That may work, but it's easier to install a normal siphon break on the water intake. Position it so that you can put your finger on it while you pump the head. By taking your finger off the air inlet for the last few pump strokes, you can leave as much or as little water in the bowl as you want.
When I installed the head, I also put in a new holding tank. Ronco (ronco-plastics.com) has a catalog with a huge number of different tank configurations so that you can get one that will fit just so, with no wasted space.
Festool/Tanos makes a line of storage boxes that work well. These might not be to everyone's taste, and they are expensive, but they stack and lock together nicely. Once they're stacked and locked they form a unit that's easier to restrain. This way you can fill something like a hanging locker or an unused berth with a tower of boxes.
I have no serious complaints about my Katadyn watermaker — it works as advertised. I may be more sensitive to salt in my water than some people, but I do still want bottled water for drinking.
Several people told me that, without question, one really needs a watermaker when cruising the Bahamas. This is not true. It is true that some places charge as much as 50 cents for a gallon of water, and it may not be very good water either. I found that my occasional overnight visits to a marina allowed me to keep my tanks topped up. If your boat has a decent amount of tankage, and your usage is modest, then you don't need a watermaker.
I've been happy with my Garmin instruments, with one outstanding problem. The autopilot works wonderfully when it works, but I did have a warranty issue. The linear actuator is the "Class A" unit, make by Jefa. This is a relatively new item sold by Garmin, and there may be a few kinks for them to work out. Inside the actuator there is a sensor which tells the controller how far the actuator extends (the position of the rudder). The sensor malfunctioned, and Garmin sent me a refurbished replacement unit. A few months later, it broke too. The long-term solution is to install a separate sensor.
I also have a Garmin radar unit. So far, I think that may have been unnecessary. I've only used it a few times, and never in a situation where I absolutely had to have it.
All of my instruments are Garmin — chartplotter, depth finder, wind indicator, radar and autopilot — and they were easy to install. Everything plugs together in a straightforward way, and it all worked right off the bat. Several professional installers tried to convince me that "a layman" couldn't possibly install all this stuff. Don't believe it.
One item you might want help with is the actuator for the autopilot. This is what moves the rudder, and it needs an arm on the rudder post, along with an anchor point against which it pushes and pulls. This requires some fabrication, which you may not want to do yourself.
I've been happy with the Lewmar anchor windlass, although the solenoid that came with it was sorely lacking, in both durability and capacity. I upgraded to a larger solenoid. Lewmar sells a wireless windlass control that's worth having, although it is expensive. This kind of wireless control (nothing more than a switch, really) is simple and there's probably an inexpensive third-party option. It is possible to buy a sort of crank handle to operate the windlass manually. I haven't used it "for real," like if the electric motor died. It works, but it's barely adequate.
I have 400 watts of solar panels. These are rigid panels, and cost something like $1.50 per watt once all of the wiring is included. Each panel passes through a seperate Victron 75/15 MPPT controller, and these are then fed in parallel to the battery bank. There has never been a problem with having enough power, and the system includes a fridge, freezer, autopilot and other instruments, plus I often run a laptop and keep cell phones, iPad and other gadgets charged. In fact, for quite a while one of the solar panels was disconnected, and I managed just as well with only 300 watts. It is true that if it's been rainy and overcast for three or more days running, then I avoid using the laptop or charging cordless power tools.