I think that the informations on the two tabs "buddylist" and "view groups" are quite redundant.
The first shows the name of the buddies and the online status, the second furthermore the number of buddies and a link to the buddy’s posts.
The main difference is that on the second tab the buddies are sorted by groups.
My proposal is to remove the first tab, to rename the "view groups" to "buddylist" and let the user choose whether he wants to see the groups (or not) by a checkbox.