Maybe I'm the odd one here, but I do really well at GR. Better than I do at istock or fotolia each month.
My only gripe is that there is a bit of a unique community aspect to GR and all of the Envato sites that can become difficult to manage. They have a commenting system that allows anyone (regardless of whether they've bought the file) to post questions and comments. Most questions are about fonts used, the make-up of the file (formats, layers, etc), etc. Because the questions and comments are publicly viewable, including by prospective buyers, I feel inclined to try and answer them all. Which of course is time-consuming. And despite trying to add more detailed information to the image descriptions and FAQs, people still ask questions that are already answered. I clearly state the file formats included in all of my images (AI, EPS, JPG) but will always get the question of whether a PSD is included.
On top of that, I occasionally get negative comments that I need to report to the site to have removed. One was about someone suggesting that I copied the image from someone else (the person I was accused of copying had, in fact, copied me and I was able to prove it). A few others were from people just unhappy with the files for reasons beyond my control (lack of Photoshop compatibility).
It's an annoyance, and for the other marketplaces I get the need for the comments section. It's necessary to be able to ask questions of a file author when it comes to WordPress templates and things like that. In the case of vectors, so far I've only found it to be another problem I have to deal with on a daily basis. My earnings are good, so for now I'll deal with the annoyance of checking for new comments every day. But long-term I wonder if this is worth the time.