The user search function in vB is pretty powerful. You can search for users based on post count, IP, email address fragment/domain, registration date, etc etc. Brilliant.
In comparison, the prune option is very minimal and a big disappointment. Is there a reason why vB doesn't offer the same kind of functionality in Prune as it does in search? It would be very handy to be able to delete all the accounts using a particular .ru email address or all accounts signing up from a xxx.xxx IP.