MicrostockGroup

You'll find that every agency has complaints here about rejections for images that were accepted 'everywhere else'. It used to be more prevalent for iStock, leading them to say that their standards were higher, but over the past year, I've often read posts here that say other companies reject files which were accepted on iStock. I guess it's part of the learning process.
That's not to say that they never hand out 'odd' rejections. However, there is a good critique forum where you'll get honest criticism, and there's a Scout system of arbitration, but it's generally taking several months right now (and you only get three Scout tickets a month).

I think it is more of a 'reject at a whim' button...

sorry, but your experience contrasts mine and that of the thread originator.