I've belonged to this place for a couple of years now. Before that I went to the Sun Prairie YMCA and before that the east side Princeton Club (we lived on the east side and then moved to Sun Prairie).
I like this place. The locker room is clean enough, the front desk staff are fast to check me in, and the 'waterpark' part (of which we are very new members) is fine.
I nearly always bring at least one child when I come, and the nursery staff are mostly a great bunch. My older kids are taking part of the summer daycamps, and everyone I've dealt with for that has been great. I've never eaten in the restaurant and so have nothing to add there.
Mostly I use the cardio equipment upstairs (they have bikes, ellipticals, and stair climbers, but I'm all about the treadmills). Nearly all the cardio equipment has its own little tv set.
I haven't taken any classes so far, though I'm eyeing the Zumba (pray for me) and the yoga. I'm intimidated by the Spinning classes but may yet grow a spine. They seem to have a lot of different classes.
They own the hockey place across the street (a new one coming up by the high school) and my understanding is that it will be razed and more parking added. I don't think the parking situation is terrible now, but I try very hard to go during non-peak hours (I am lucky to have a choice most days).