I downloaded Lightroom 4 Beta after receiving an announcement email from Adobe. I sat on it for a week before reading a tweet from Petapixel, who was in turn quoting Scott Kelby.
Mr. Kelby thinks that Lightroom 4 Beta is the bee's knees. He raves about how my photos will look better processed in Lightroom 4. "Period."
With that kind of ringing endorsement I installed the beta and fired it up, thinking of how much better my photos were going to be. Period.
But then I was bluntly informed by Lightroom 4 Beta that my Lightroom 3 catalogs couldn't be opened by Lightroom 4 Beta. Period. So, unless I want to run with two versions in parallel, I'm afraid I'm going to have to wait and continue to turn out less than stellar photographs with Lightroom 3.6 until they release a version of Lightroom 4 that can read my old and busted LR 3 catalogs.
Too bad. So sad.