In reply to 19G:
Depends what you are climbing. Smearing with your feet and using smaller crimps and slopers you are technically closer to the limit of what is technically possible so water is a big problem.
If you are climbing in big boots it can make next to no difference since you'd be edging most of the time anyway and if you are capable of climbing it in big boots you can probably climb it in the wet.
If you want to have a good day out and battle against the elements then go climb in the rain - resort to a bit of french-free if need be. This is probably closer to the original "struggle against the elements, its a challenge" spirit of climbing than the more modern technical experience and has probably been replaced for those that want it with Scottish winter. If you can find it there is some great archive footage of climbers in the past climbing, in a style we would think of as rock climbing, in terrible snowy conditions on the cobbler. I guess having made the journey out of the big smoke there was nothing else to do but make the most of it!
I think what I am suggesting is that as a technical graded exercise: don't bother, the holds have been lubricated with water and you won't be able to use them . As a fun day out testing yourself against adversity it can be great fun... but there is a reason why most people don't climb in the rain. Go, try it and have fun finding out!