This is an ancient thread but I'll play along.
I tried to get accepted at iStock many years ago and had one of my three files accepted. After a few more attempts I gave up and decided that this "stock" thing wasn't for me. For some reason I never thought at the time that there would be other places to submit my work.
A couple years later after becoming aware that there were places other than iStock I started submitting my work and making some cash.
After just over a year and a half I'm closing in on 30,000 downloads at Shutterstock alone. That one file that was accepted at iStock? It was one of my first ten at Shutterstock and has been one of my least popular images with a whopping 8 downloads. Those files that weren't good enough for iStock have been downloaded hundreds of times.
To put it simply... F#$% iStock.