I could never take a shine to the original version of Capture One LE that came with my M8.0. It had (to me) a confusing interface, and sharpening that either couldn't be turned off, or else I never managed to understand how to shut it off. Also in the beginning I was shooting everything @ ISO 160 and "pushing" it in the raw developer, and C1-LE had less stops on the slider than ACR. So for quite a time I used ACR. I still have CS2, but probably will upgrade to CS3 (I don't mind to stay one generation behind and save myself $$$$). It worked very well, better for me than C1-LE.
Then I happened to attend a get-together sponsored by Dale Labs, the Hollywood, FL Leica dealer, and Dave Farkas showed me some stuff he'd done, urged me to do the free upgrade to C1 v4, and downloaded me his M8 profile that he made in his studio. Also I started following Dan States' advice in re: noise reduction settings, and stopped shooting everything @ 160 and pushing. So as of now I'm back to C1 (v4) and rarely ever touch Photoshop for M8 files.
I know there are many opinions, and a lot of people seem to use Lightroom and (I guess the Mac guys ?) Aperture. So perhaps it's like lens choices, you really can't rely entirely on others' opinions, you need to use what suits you.