I've used Envato for years to purchase everything from WordPress themes to sound clips. It's an invaluable marketplace.

I agree that a LOT of the themes in Themeforest are rushed to market. You really have to do your homework and read the comments both with the theme, and look at how the developers handle their own support.

Generally, if there are any initial bugs, I only need support once or twice. After that I assume down the line I'm on my own, and I'm fine with that.

There are a few developers that have stellar support, and still push updates on themes I've purchased 2-3 years ago. Typically I buy from the same developers for this reason.

If I had an issue with many of the themes there, it's that they try to be everything for everybody and include too many unnecessary style settings and options that even a noob should know how to do with CSS.

Other than that, I live Themeforest. You just can't trust every theme just because it looks good.