I took my drysuit on Whirlwind in early December - people laughed at me at the start of the week - less so by the end!
I did take a 5mm wetsuit and vest to go under it just in case of problems (fortunately had enough luggage allowance for that) but it didn't even get wet! It means you are the first one in to meals too 'cos it takes far less time to get in and out of
If you do take a drysuit don't forget the talc (I had to borrow some all week because I forgot it - doh!). Also mine didn't like being hung on their hangers on the dive deck because it has permanent shot ankle weights and the weight was putting a lot of strain on the joint between the neckseal and the fabric when it was hanging. So I ended up hanging it over the railings that stop you falling down the stairs onto the dive deck from the sundeck above and tying it on if we were moving - Skez and Katie (the guides) will know what I mean!