I use 3 gallon critter keepers as my regular tanks. A lot of tanks are made of acrylic. They're fine. I like them because they're lightweight. And critter keepers provide lots of horizontal (rather than vertical) swimming space, which is perfect for bettas.
Heaters aren't an issue. Our body temp is 97.6F (37C), and we don't melt plastic (acrylic) when we hold it. So using a heater that brings water temp to about 79F (28C) is going to cause a problem, either.
IMO, the only downside to acrylic tanks is they can get scratched easily. And if handed roughly, they can crack.
In terms of using one as a hospital tank, they're fine. Bettas are often calmer in darkened conditions, so I wouldn't bother with a light. And many medications require that filters not be used, since filters would absorb the meds....
Last edited by LittleBlueFishlets; 03-24-2013 at 09:12 AM.