Yes, Iris is very good. However it is somewhat involved to get familiar with. But once you are over with initial pain, it rules..
If you use Canon DSLR, then you most likely also have DPP (Digital Photo Professional) that comes with camera.
I use it almost exclusively for post-processing (curves etc, after stacking in DSS).
Also have a look at this thread, Fitsworks looks interesting..
http://www.iceinspace.com.au/forum/s...ad.php?t=52140