First year breeding I didn't use a t-stat and temps were all over the place. You need to do alot of adjusting to keep it stable. Second year I used the Hovabator with a t-stat and it was much better.
I now use a small fridge converted to an incubator with my Herpstat and I love it.
The choice is yours in the end but remember that you get what you pay for.
I only used the Hovabator because I already had it. I also know many people that use them problem free but as sited on this thread it's obvious some have had problems.
Gavin