I've been using Envato for a few themes and plugins over the last year as a WordPress site designer, not a developer. I take the time to research the product I'm purchasing. If the developer's demo page is poorly designed or the comments raise red flags, I stay away.

My success rate for themes and plugins is pretty good. I look at the ratings with a discerning eye. I ask pointed pre-sale questions to see if the developer is quick to respond and can communicate well. Currently, I have no need for multi-language or eCommerce so that is a big help.

I also buy and/or use themes and plugins from theme/plugin shops and ones found on the .org repository.

Mostly, I find a theme that I like and use it for several sites, tweaking the css as I go. I would like to code my own theme, but just don't have the time. I'm a designer. I understand code but don't want to deal with it unless I have to.

Theme Forest and Code Canyon have provided me with some products that my clients have been happy with and are invaluable in some situations. I can let go of the duds because I took a chance on a low investment.