In the Quicksilver forums today I stumbled across the link that brings you the very latest, more bleeeding-edge version of Quicksilver.
Apparently, setting the “Application Update Type” to “pre-release” in Quicksilver’s Extra Settings doesn’t actually deliver the most recent version.
However, this link does: http://getqs.com/dev/ 
Quicksilver β50 Bulldog (3787) looks a lot like its precedessors. After thirty minutes of poking around, the only new things I have found are the swish new menubar icon (a Q with a fancy tail) and working previews for the app’s various interfaces in the preferences.
But a large part of the fun with Quicksilver is never knowing what new thing is just around the corner.
Obviously, the pre-pre-release version is not fully polished. So there’s no complaining if it doesn’t all work out as expected.
Great find!
Not sure if they were in the b49 version but I’ve found a few new interface plugins. The menu interface if very slick and minimal!
The menu interface has been around for a while, I think.
It looks good, but requires too much squinting for me to use it.
Most of the changes in b50 thus far are Leopard-related fixes.
Think…. QuickSilver
Think…. Core Animation..
Think…. How Cool That Will Be!!!!
There’s another minor difference: The “Customize” button, earlier located to the left of “Command Interface”, (in Appearance, Quicksilver Preferences) has now been removed. The function didn’t do anything in the earlier versions (just a nice button that went blue whilst you were clicking it), so it will not be dearly missed.
Somewhat reminiscent (if not the same icon) of http://www.artofadambetts.com/weblog/index.php?s=quicksilver
[...] Quicksilver alpha builds, B50 Bulldog: ”Filed under: Software, Freeware, Universal BinaryHawkWings brings us two quick notes about everyones favorite OS X do-everything app, Quicksilver. According to a thread in the QS forums, contrary to many a users’ expectations, setting QS to check for pre-release versions does not get you the very latest bleeding edge super Xtreme sub-alpha builds of the application. Instead, if you feel you are Xtreme enough to handle pre-pre-release builds of Quicksilver, head on over to the GetQS.com developer page. Speaking of ultra-alpha versions, Quicksilver B50 Bulldog was recently released, and although it doesn’t sport much in the way of new features, it does have a sexy new menu bar icon. “ [...]
@Thomas – nice find. Thanks for pointing that out.
@Kyle – Spooky. I think it is the same. Thanks for the link.