I will let you decide. But this is open source so that should at least make it a rival of PS just because of the price
http://lightzoneproject.org (http://lightzoneproject.org)
Might be free, was a pain to install. I thought it hosed my system, thanfully not....
I played around with it a bit, but after learnign the Adobe Interface, I'm not keen on reprogramming my brain to use this software...
Thank you for the feed back Woolly! If anyone has the ability to dissect a program for photography and find its issues, I think it would be you!!