www.iFourWinns.com

Number one point:
If it has the XPD composite drives, forget it. They are trouble and discontinued.
If it has the SX drive, then fine, they are very good.
Salt water.
Well here's my take on it. I have found that in my area, the available anti fouling paints do not work well. If you left it in from May to Oct you'd have a ton of growth on the drive and transom. Eventually you get barnacles in the water intakes that causes mild to moderate overheating. If the anti fouling paints work in your region, then its do-able. For me I have taken to pulling the boat in early August, cleaning the drive, cleaning out the water intakes and re-painting the drive. Its much easier this way.

If you are in a marina, corrosion from stray currents can be a problem. I keep mine on a rotating mooring and have not had big problems with corrosion, esp for the advanced age of the boat. I do advise extra careful maintenance. As in:
Careful monitoring of the exhaust system, figure on replacing manifolds and risers every 5-7 years. If you see rust stains on the outside of that joint, then figure it could be leaking inside and you need to take a look.
The drive should be pulled each fall and all the maintenance has to be done. Bellows checked for water, gimble and ujoints greased, driveshaft greased.
Winterizing: if raw water cooled in salt water you should be manually draining and then back filling the engine and manifolds with the best -100 antifreeze.

I have done this for years and have not had major problems. But keep in mind an I/O power package is high maintenance in salt water vs straight inboards/v-drives or outboards.

288 with 5.0 Gxi and SX drive, no shortage on power. You'll love it. The electric opening of the engine bay is very nice, but the space between the engines is limited, so maintenance can be tough when working between the engines. The front is easy to access so, fuel filters, oil filters and serpentine belts are easy to replace. Trying to do work behind the engines is hard, there is not much to do, hydraulic resovoirs, steering and a few other things. Electric, the routing of wires behind the panel is untidy, but not hard to work on, the electrical schematic is easy to follow. I installed a chart plotter myself and it was fairly easy. I would avoid running ac for extended periods, it will wear parts out and the strainer will need regular cleaning. In my view its a waste of energy. I place two moisture absorption buckets in the cabin when I am not using the boat, smells nice, works great, inexpensive. I have no experiance in in long term sea water docking, but I can imagine that it is a challenge to keep things clean and control corrosion. Despite this I repaint my outdrives every year, and they still look new. It's hard work, but I enjoy it. I use a very specific procedure and materials to ensure good adhesion. If I docked in salt water, I'd use boat lift. 288 is a big boat, so that'll be an expensive excercise, but I think in the long run it'll save a lot of money. Is the 288 you're looking at a fresh water boat? If so, I'd really spend time examining the areas that are prone to corrosion.