Royalty images - uploading your photos

Does anybody have experience with uploading your own photos to services like Veer or fotolia or depositphotos or istockphoto? Are there some that are better for some types of images? Some better or worse to work with? Any recommendations of others to look at? Do people commonly stick with one service and get paid more for exclusive rights or upload to multiple to increase your odds at the cost of a lower fee schedule for non-exclusive?

Thanks!