I've placed 10 test stock photogrpahy images in many sites, Up till now I only made sales on Fotolia!!
Not sure why is that, they are the same images, but only selling on Fotolia, I am thinking to move exclusivly with them.

Have been many changes lately on Fotolia:
- the subscription program – subscription- you can’t opt out your images from this; many photographers hate it since it is paid so low. Also, a bad thing to this- subscriptions download need to be four (4) in order to be counted as one regular download;
- exclusivity-well some photographers like it, and many not- why one should work only with one microstock agency?
- changes in terms of the price of the illustration- they have adopted the Istockphoto model and, if you’re skilled, you can make also some money in this way;

Other minus points:
- really strange reviews. It is getting harder to get photos accepted there. You don’t get a clear feedback why your image was rejected (many of you already get that list where you can choose from different things…).
- the infinite collection: let’s be honest and have a look there : many of them suffer from quality problems;
- free image collection : comparing to 123rf (where you can give for free at the 400X300) dimension, here you get images at high resolution for free. OK, not free, but some of your already accepted photos can go there for 0.5 $ each, if they are with no downloads in the past 24 months;
- if your images were rejected, you can’t get too much feedback from the forum. Posted image there is quite small and you can end up that your idea is copied and somebody else is submitting and it gets accepted!

Good points:

- you get sales: you can establish the price of your photos (with some limits and this, in respect to your ranking);
- ranking :many sales will lead to an increase of your ranking and also the price intervals for your images. Unfortunately, this will not apply for subscription sales.
All in all: work hard for your portfolio, look for the best images there and try to be original.