I find I can get a sharper image from ACR/PSE than DPP, and more importantly, a less noisy image. DPP does a sub-par job on noise. If I shoot at high-ISO (3200 on a 7D for example), and crank the Chroma slider all the way to 20, it's still filled with chroma noise, and the luma noise reduction hurts sharpess much more than ACR's. The controls in ACR for adjusting fill light, etc work nicer than trying to get the curves just right, and the magic 'clarity' local contast slider, is awesome.
I've stuck with DPP for the last, what 2.5 years. I've just discovered how nice ACR can be this week. Oh, and aside from the missing 'go back to ACR' button, ACR needs a click to set white balance button.
As long as we're in semi-gripe mode, ZoomBrowser, when I say 'edit with external editor' don't tell me I need to convert my CR2 to something editable first. DPP and PSE can both load your CR2 files. Just launch them, thanks. If you need to babysit, give me a 'this application can read CR2' checkbox when I'm adding image editors.