I downloaded the C1-4 beta. I installed it (took forever because it required running and installing .NET), ran it for fifteen minutes, and uninstalled it. Not a promising start. It seemed slow on my system (Win XP Pro, dual-core Opteron, 4GB RAM) when starting and loading a folder. At on point in working on a 1Ds2 image, the preview just froze and remained pixelated. But the worst thing: it supposedly supports Canon Mark III files. It rendered the thumbnails, but that's where it stopped. I tried opening several files. Each time I got the "Loading..." message, but no image.
I always liked the quality of files from Capture One, though it seems antiquated by Lightroom standards in the adjustments department. I do feel it produces better files, in many ways, than Lightroom, such as smmother tone, sharper without artifacts. Unlike Lightroom, I love that you don't have to import files, you just open them where they are. I'll be curious about the Pro version. I'm unimpressed by the current beta, but will keep my mind open