YMCA Town Lake - I think people like it, but you have to be a member.
Texas Swim Center - awesome, but kind of pricey, bad parking, and not great hours.
24-Hour Fitness Hancock Center - I didn't care for it because people didn't shower before entering after exiting the sauna. theoretically, it would be fine, but it grossed me out. it's a small, 25 m pool (3 or 4 lanes)
Lifetime Fitness - don't know much about it, except it's way northwest. supposed to be neat.
Body Business - don't know much about it, except they use bromine, and some people are allergic.
Those are all I can think of. Lost Creek has early morning masters to avoid the sun. I LOVE swimming there, but it's not practical with the baby and Brad. Many City of Austin pools are free during the summer and have lap swimming beginning at 7 am. Stacy Pool is free and heated year-round and has lap swimming all the time, but it's pretty far south. Barton Springs opens at 5:30 am and is free for some of the morning and late evening.
Please leave me a comment if you have suggestions or more info.