AD has pretty much no serious replacement, but MSO is for me as bad as everything else out there. Office in general constantly crashes and the only thing that is reasonable in Outlook is the calendar integration. It's so bad, that in 2007 it still didn't have a good threading view of messages. Communicator is a joke where you can't even do local list search - you either have to query global company address list, or manually scroll through your contacts...

In general no - I can't agree they're "really, really way better" than OS replacements. They're better for some people, worse for others.