Re: Lack of integrated email/contacts/calendar?
"I can only assume that you have never used Outlook / Lync / Unified Messaging - together with Office / Sharepoint / Yammer, etc?"
Outlook is an appalling, bug ridden product with some serious usability issues and total disregard for any established standards. I'd more than happily shoot, multiple times to be sure, the developers of Outlook's HTML renderer, quite apart from the intentionally broken IMAP support, or as noted elsewhere broken anything non-Exchange. However the worst thing Outlook... is that it is better than anything else equivalent. I may be wrong on this, but so far I haven't come across anything close and I've tried a lot of alternatives - only Thunderbird came close and the UI of that was designed by idiots.
Lync may appear to have a clean interface, but it's amazingly bug ridden, bloated beyond belief and just performing simple tasks is an exercise in frustration. Once it's finally started which tends to take a long time.... and yet somehow after all this it is better than Communicator, but that isn't because it's good, just that Communicator was so bad. However to be fair, IM clients don't have a good usability pedigree and bolting extra functionality on top of very poorly designed, or intentionally limited interfaces, is not always an easy task.
Sharepoint is the devil's work. For good (sanity) reasons, I avoid this bloated, unwieldy monstrosity whenever I can. The security scheme alone makes the hatchet job of normal windows file/print security look well designed. As for all the ridiculous bugs that relate to data that are still in place... arrrgggh. On the other hand, if you want a quick alternative to shared spreadsheets that are used to do little more than record data, it does quite a good job and while the document management feels entirely cumbersome and has been implemented in a ridiculously inefficient manner, it does sort of work.