I think the Hova-bator's work fine. My first year I only had one clutch and was feeling very uncomfortable at the thought of making my own incubator (also not very handy...). So, I purchased a hova-bator. I didn't run mine on a thermostat either, I just used the built in one. It did flucuate a little (like from 88 degrees to 90 degrees), but it never got wildly too cold or too hot. It recommends putting it in a room that doesn't have a draft. So, I closed the vents in a spare room and kept it there. I hatched 5 perfect babies out of 5 eggs. I think it could easily hold two average sized ball python clutches. The only problem I had, was that I had an egg that I couldn't seperate that was on top of the other eggs, and it got really dimply from too little mositure. However, that's not really a hova-bator issue...more like a egg box issue.

That said, this last year I was expecting more clutches and had a better idea of what actually went on in the incubation process. So my room-mate and I found wine coolers on CL...pretty cheap...like 30 each or something maybe less, bought the heat tape from reptile basics, and made our own. It worked great and we hatched all of our babies again this year. The only problem we had was that we installed a fan, whatever one that is recommended in the DIY thread, and it overheated and raised the temperature of the incubator to like 96 degrees!! But, after we figured out what was going on, we just took it out and dealt with the temperature gradient.