Nobody uses Photogenics (on the PC and Amiga)? I could not live without ACDSee, personally. I use ACDSee 32 v2.4 and despise the 3.x versions of it...not even the same program, IMHO. I heard (from a beta tester) that the authors are returning to the 2.x style in the near future. It's great for fast pic conversions, system navigation, image flipping, full shell usage, copy/move, etc. and most everything else. A poor-man's Directory Opus, but with instant image viewing and previewing, which Opus doesn't offer. A combination of the two programs would be perfect (in other words, if ACDSee had dual windows, it would be the shit!) I use it at work on a variety of machines and Windows versions and it has a tendency to just crash for no reason no matter where it's run, though.
Photoshop has a steep learning curve, but once over that hump, it's indispensable. Haven't tried Fireworks, but since I so abhor Flash and Shock, I'd probably hate it...