For RAW processing, I would suggest first trying DPP which should have come with your Camera (also download updates to it as well from Canon.) Some pros even still prefer it to Camera Raw (although they're liking the way Adobe's Lightroom is looking, but expect it to cost some bucks when out of Beta.) If you feel that DPP doesn't do enough for you on the RAW side, then look into other options.
Don't know what's in Photoshop2 or Arcsuite, but Photoshop Elements covers most of my processing needs lately (I'm using version 3, but version 5 is out now.) Especially like the healing brush. And for those times that I need curves or some other options that Elements lacks, I use The Gimp (free at gimp.org). (My version of Elements came packaged with my WACOM tablet - all together under $100... not a bad deal!)
BTW elements (versions 3 and up) can use the Camera Raw plug-in (albeit limited compared to Camera Raw of CS2 users.) As far as I know, the GIMP doesn't handle raw at all, just your standard image formats (plus .psd photoshop files)