My fiance, friends, and I had an absolute blast here - it was really a highlight of our trip to Vegas.
Got the groupon for 4 people for $75. I emailed the company regarding sizing for myself (6'4 290 lbs). I got a friendly and swift response from them saying I'd have no problem fitting. Well, as it turned out, I did fit, but it was very tight...they said anybody up to 350 lbs an a 44 waist could fit, I'm 290 with a 42...can't imagine adding another 60 lbs and still being able to fit.
In any event, the staff was very friendly and made sure that riders were being as safe as possible - they were very hands on. I love that they give out the printout of how everyone did after the race - very cool how precise it is.
I'd definitely recommend going here and I'm sure I'll go back next time we visit Vegas. I would also recommend calling ahead of time to make sure they don't have the place booked for a party.