I've had better acceptance at Alamy than the Micro Sites. As of today I'm still at 100% acceptance. I can't say that about any Micro site. However I submit only a few at a time because of the way they reject. If you upload 10 photos and they reject (1) of them, they also reject the other (9). They have very strict image requirements too. I would suggest reading their requirements several times before you submit anything. I do exactly as what they tell you to do to each image and so far I have had good luck. On the other hand I've had no sales there. My portfolio is very small and not that unique but I wanted to try to see what would happen.
Later this spring I'm planning to shoot for a week or so with Alamy in mind. I've yet to upload any RM. Everything so far has been RF. I'm not sure that was a good choice.
Good luck with Alamy, I hear about photogs having great success there. RM shots can earn as much in one sale as some micro sites gross in a month for your entire portfolio.