Bibble Pro impressed me in many ways. I evaluated it, along with 5 other software early last year, giving them a catalog of 18000 and working with them over a 3 month period. The only two that were outstanding were Lightroom and Bibble Pro.
Bibble Pro is considerably faster and with their search interface is it easier to create powerful searches. You can also work with unmanaged images with is a nice bonus for some tasks or when other people send you images to look or modify for them.
In the end I had two issues with it, one was some EXIF strangeness and the other was that it could not import large panoramas (a work-around is possible but time-consuming). The actual showstopper for me was that they did not answer my support calls, emails and faxes, giving me the impression that they do not care much. This may be an isolated incident but something to consider.
Finally I choose Lightroom and I am happy with it. It is powerful, flexible and mostly intuitive. There is also a lot of information and literature on it as well. While I really preferred Bibble's interface, I cannot say there is anything truly problematic with how Lightroom works. The lack of a fit-to-full-screen view still bugs me though.
Note that there are many features that I do not use and which I can therefore not compare: printing, slideshow, publish to website (once I did in Lightroom). I also only do extremely basic changes to my images, most cropping, some rotation and color changes.
You can read a basic overview of the DAM aspect of Lightroom, Bibble Pro (and a several other software) in my DAM Software Article. It may help you compare them.