I'm a member of the one in Temple Bar. The decor is really something else, more akin to a nightclub than a gym. There are what I would consider a huge amount of treadmills/cross trainers. The weights machines are adequate, but both the free weights and warm-up areas are way too small. I only use these first thing in the morning when it's quiet, but in the evenings these areas are packed. However, there are notices saying that these areas are going to be expanded to three times their size during the summer (I'm not sure what this will be to the expense of). I've never had to wait for a cardio machine at even the busiest time (evenings shortly after the new year). Haven't done any classes, but know people who do and they like them (yoga and pilates classes are not included in membership, but all others are). Only use the pool the very odd time, and again I've only ever been in there first thing when the whole gym is quiet, but it's not huge so I'd imagine that it gets quite crowded during busy times.
I don't like the fact that weekend opening hours are from 10-7. It's pricey enough. I'm paying €69 monthly, but I don't really mind as I do tend to go quite often because of the location. When I joined, there was a €100 joining fee which was due to double the following week. However, I have seen the current pricelist and I don't think it ever has increased (they are just using this to get you to sign up straight away). Membership includes use of the Dun Laoghaire branch too, but I haven't been there.