I've been very pleased with a few of the projects I did last winter. First and foremost, the Frigoboat keel-cooled reefer has been very nice. We placed some passive insulation (a sheet of blue-board) between the cold box and the rest of the fridge; the digital thermostat makes it very easy to set the temp exactly where you want it so it's cold enough to make ice but not so cold as to freeze veggies. The compressor is quiet, as Jon and others have noted, and uses about 35 AH per day. That's low enough that, with the solar panels deployed, I've been able to leave the fridge running even while we're away from the boat for a week or more. It's nice to be able to leave butter, cheese, fruit etc aboard, and of course have ice handy when you arrive back at the boat ready for a G&T.
The heater that runs off the engine is equally nice. It's cheap and easy to install; there's little reason not to put one on for those of us who cruise in cooler climates.
Finally, the PrecisionTemp on-demand propane water heater has been a big hit with my wife. It is set to about 104F to save having to run dual (hot/cold) lines and mixing faucets - a lot simpler. One shower line runs to the cockpit, the other to the head. It's easy to fill a bowlful of warm water for washing dishes. The PrecisionTemp is a bit pricey, but is a very nice feature especially given that we try not to run the engine much (I did not replace the HW exchanger after it died last year). I guess my one complaint is that the temp seems to fluctuate a bit, maybe due to uneven water pressure, but it's more an annoyance than a real complaint.
This winter's projects include some engine work: new transmission (keeping the old as a spare), engine mounts, and flexible coupling. I plan to remove the Lavac and holding tank and install a Nature's Way composting head; that will free up quite a bit of space for shelves where the pump, tank, Y valves and hoses run. I also plan to install a supplemental 39 gallon water tank under the aft end of the V berth. I plan to add Navtex and AIS (unsure whether transmit/receive, or receive only). Of course I also have to deal with the main fuel tank which started leaking last June.