Some groups are more active than others, depends on how people feel about them and effort they are prepared to put into making a group a success
We have found the same! The groups are very hit and miss
As things stand, people mostly use the groups as an interest marker, and for this purpose they can be a very effective tool.
When perving profiles I always check what groups people have joined, sometimes their group selection can say more about their sexual preferences than the rest of their profile put together. But as for conversation... no, never seen any current ones in any - but then I wouldn't, because I don't check! It's a catch 22, certainly and underused feature but good enough for grouping like-minded people for those that care to have a browse-through!