pediatron,
I was on a Dancer liveaboard several years ago (before it sank) and we dove the blue hole on about day 4. By that time, everybody was comfortable w/ each other, their equipment and we had a great DM.
Out of the 18 divers, about 6 decided not to go on the dive for various reasons. It's ok to say no.
We spent over 30 min. going over the dive plan. We discussed how deep we would go, how long we would stay, how close together we would stay, how long and where we would safety stop, where we could find extra gas, etc. etc. etc. The dive plan lasted longer than the dive. We were asked not to do another dive that day.
The dive lasted about 30 min and according to my computer, we maxed at about 135 ft. It took about 5 min to get down, we stayed about 7 min. and spent the rest of the time was spent ascending and doing our stop. It was and is my deepest dive to date. Personally, I think it was one of the most boring dives I've ever done. There wasn't anything interesting to see (in my book) and the dive was over in a 1/2 hr. Everybody returned with plenty of gas. The only fun part was free falling from 20 to 135 ft. in 100+ ft vis. That was ok, but now that I've done it, I'll not do it again. I'd much rather have done 5 shallower one hour dives that day on a reef.
If you are comfortable w/ your skills, equipment, DM, buddy, the dive outfit's ability to care for you in the event of an accident, and you want to log a deep dive, go for it. Remember, you'll have a few days to get comfortable again in the water b/f the hole.
The water is warm and clear and it's a good place to do a deep dive (other than the remote location). However, if you feel the least bit hesitant (women have great intuition), pass it up. If your significant other puts pressure on you to dive it, slug him.
Mark