This plugin is saving our site from piles of splogger registrations. It is to Buddypress what Akismet is to WordPress, in my opinion.
I'm just experimenting with BuddyPress, and I love it that WangGuard keeps my database free of spammers except, perhaps for the occasional spammer with reasonable intelligence who registers personally.
I had Registration disabled on our busy blog and allowed posting by non-registered users. (Worked fine because of Akisment & Conditional Captcha -- a powerful team that ensures we don't have to look at spam and legit users don't have to fill out Captcha's.)
Before disabling registration, we had accumulated thousands of users in our database, with a high proportion of spammers. Thus when I wanted to experiment with BuddyPress, I was wary of allowing registration, which is necessary for BuddyPress. I had already deleted all users, but WangGuard would have done it for me if I had not.
Now WangGuard ensure that only legitimate users enter our database.
I'm very pleased.