OK, been trying out the trial version (30 days), seems pretty good so far. It's loading images faster than Lightroom 3.3, which has a penchant for stalling when loading views (although that could also be because it's got the whole 60 GB of my RAW folder in its database). The interface is different from LR, but reasonably intuitive, didn't take me long to get my legs at all.
Sadly, my 4870 isn't supported for OpenCL, but as I'm moving to a new build next month, is not a crucial factor in my decision process.
The noise engine is not as good as Lightroom 3, which does a great job of killing noise while preserving detail. Then again, I might get better at tweaking it after some practice, since I've been using LR for a couple of years and Capture One for only a few hours.
It's not as noob-friendly as LR when it comes to preset effects, which I've found to be a good way to get close to the effect I want to achieve. Unless I haven't found it yet. LR is good enough for me that I rarely have to dip into Photoshop, not sure if Capture One will fill that role for me.
Verdict: Interesting (so far).
Wind, Sand and Stars.