I just tried the Adobe Camera Raw 2.4 beta out (with Photoshop CS). Works like a charm. Much better than Dimage Viewer (hasn't crashed yet, is faster, has more settings). Looks better than MRWFormat too (which had lots of settings, probably a few too many, and had it's share of crashes as well). Automation seens to work (record it once, apply it to zillions of images).
The only nag I have is that when I move a slider (for, say, color temperature), it refreshes the preview for every step the slider moves (or, after every digit I type in a text box unless I type quite quickly), and that takes a second or two. If you have a faster machine than my old 1.3GHz Duron, it shouldn't be a problem (a 3GHz Pentium should be 3-4 times faster).
There are settings for correcting chromatic abbheration (blue or red color fringes at the edges of the image, especially in cheap zoom lenses) and vignetting as well. I haven't seen any of that in the few RAW pictures I've taken so far (so I have nothing to test the corrections on), will have to see how that works later on. There, you can save presets (for example for different lenses), which should make it quite usable.
I don't know how the Photoshop CS plugins work with other applications, but I imagine this plugin should work just like any other (it's looks and behaves like a normal .8bi file format plugin).