Getting into Dreamstime
But... lets look at it from the bright side. The reviewing process itself is slow and one could be a bit uncomfortable or even disappointed to be rejected after so much waiting. I think this forces contributor to be on the right track, to think in advance, to try to judge it's own image properly before updating. You just want to be more sure that image is up to the guidelines. I found myself rejecting my own image and not uploading at all.
On the other hand, I have some images rejected by Dreamstime. But what I like is that waiting for review is worth since the rejection is well explained and you can really see what is wrong without visiting the critique forum.
So, comparing to Dreamstime veterans I'm still a baby but I think I'll stay here for a while. Dreamstime is not just image selling service, it is great resource for overall learning and developing your photograph skills.
Photo credits: Aleksandar Horvat.