If you are participating in the Facebook beta through the BlackBerry Beta Zone, then you will be happy to hear that v2.0 was just updated. This version apparently fixes an issue a lot of users were reporting regarding signing in to the app. If you aren't currently a member of the Beta Zone then unfortunately this update isn't available to you. It's never to late to sign up to be a beta tester though, so head on over to blackberry.com/beta and get registered! You may even win a prize next week for being a member of the Beta Zone as RIM is having a celebration for reaching over 100,000 Beta Zone participants.
For more details on the Facebook update or to register for the Beta Zone