i've had wow running off an ssd since just before xmas when i got my new system.
and ye - it dramatically reduces load and relog times and general load times in game (textures etc). i got a new mobo/cpu/ram/gpu also, so i cant say its purely my ssd coz now im gettin like 200+ fps everywhere with everythin on ultra and no problems at all, but ye - load times acorss the board at least are certainly noticable.
windows starts in like ~15 secs too, which is always nice.
i've got an ocz 120gig ssd with just win7/wow on it, its great