We were there that time last year and will be back the same time this year!
Yes, it IS very, very HOT and HUMID, it rains and there is also the possibility of hurricanes (we left last year just as Katrina was turning into a hurricane) but we still like that time of year!
My DH HATES the humidity and stays in the room quite a bit - we stay concierge level so he doesn't mind hanging out in the lounge at times. Sometimes he does work and sometimes he relaxes and on some days he even comes out with us for a while. The kids are 6 & 11 now and have been to the parks many times so I have no problem taking them out alone. DH generally joins us for our nightly visit to EPCOT, our favorite park.
One of DH's requirements is that we have dinner reservations every night and he always comes out for that. We also put the kids in daycare one night and enjoy a dinner alone.
Last august we found the crowds VERY manageable - there were less people there than when we went the end of June a couple of years. I have a friend who has been doing this week for a couple of years and she kept telling me how good it was but I didn't believe her

so last year I had to try it for myself.
Yes, the sweat can roll right off you - even at night - but it didn't bother me a whole lot - we were at Disney!! We also got to go to BOTH water parks, whereas one was always closed when we went in november. The parks are also open later.
I think you have to try it to see if it is something you can handle. Our oldest is in 5th grade now and it has gotten too difficult to take him out of school for Disney trips, something that wasn't a problem in the past. We also go down april vacation, which will be more crowded this year due to it being around Easter - but the weather that time of year is GREAT!
Good luck with whatever you choose!
Jill