If you goto the directory where you checked out the svn repository, and run this, it will tell you the version you currently have checked out:
svn status -u
The out may look something like this, depending on how close to current you are:
~/public_html/beta/buddypresssvn]$ svn status -u
Status against revision: 845
if you are not up to date, it will show changes between your checkout and the trunk, similar to this:
~/public_html/beta/buddypresssvn]$ svn status -u
* 844 bp-languages/buddypress.pot
Status against revision: 845
This tells me that the language file has been updated since my last checkout.
you can then run
svn up
to bring your directory up to currrent status.
If you used the zip to download a copy this will not work.
Unfortunately I’m using the zip download from the trunk. Would be nice if BuddyPress displayed the revision number in the footer of the admin dashboard
I have a text file in the root of my BP installation with the revision in it. When I upgrade, I changed the revision in the file. All I have to do is call the file in my browser and voila. I do the same with WPMU.
Sometimes the easiest approach is the best. I’ll start using the text file method for now.
On the latest version of buddypress, you can view your version in the admin now on the “buddypress” options page 
