I have to agree with all of you who have posted so far. I'm happy to do SEP over water with life jackets & rafts and an ELB in the summer. If I flew in the winter (which I don't at the moment) then I'd also consider an immersion suit as well.
Last summer, I was renting a new a/c (to me) at a new airfield (to me) and the a/c came with life jackets but no raft. So I asked around to see if I could rent one for trip with a longer over water stretch and was amazed by the number of people tried to convince me they are a waste of time and not to bother with one. The "barman" was particularly verbose about this –I tried to point out that most people survive ditching and then hypothermia is the next big thing to deal with, but he didn’t want to listen. I hate to think what other pearls of wisdom he offers student pilots who might not know better.