It is just like creating a beast with 800 heads, which will kill anyone that touches it. The result is that every one of the services you mentioned is poorly implemented in Exchange.
The real solution is to use open standards to create applications in each of those areas that can really solve individual problems. That is how software that really works is created. Thanks to M$, we are far away from a decent solution in these terms.
Integration is not a bad thing. If you don't like the way Microsoft does it -- whether it be the quality of their implementation, or their disregard for standards compliance, or whatever -- that's cool, and I don't even disagree. But business decisions are made based on the bottom line, not on ideology. If Exchange meets the business requirements, and is cheaper to administer than a hodgepodge of other technologies, pragmatically it just doesn't matter if it doesn't implement IMAP exactly to spec.
I'm not a big fan of MS, but they're just giving the market what it wants here. If you can do better, please do.
Trying to build all those services yourself using open source options, tying them all into an LDAP server, is an amazing pain. Does everyone need all of that? No. But honestly I can't imagine trying to handle the mail, shared mailboxes, messaging, scheduling, booking resources (conference rooms, equipment, etc..) for a Fortune 500 using the other options I'm aware of.
It may be "blather" to you, but it's generally pretty important stuff for a large company.
Obviously, practically none of this is stuff you can't find elsewhere. But if you know of a single other offering as complete as Exchange, I'd love to hear about it. And perhaps the biggest point of all: extensive integration with Active Directory, which is the directory service of choice in a huge percentage of enterprises.