Honestly?
I was very satisfied with Hotmail. Only thing that annoyed me was - with using Windows 7 - when I replied to or wrote a new e-mail, the page always got stuck for about 30 seconds.
When I first got noticed about the upgrade to outlook.com I took a look at it and thought "well, doesn't look as good, but let's see; they'll sure make it faster, fix the bugs and add all Hotmail's features".
Now the upgrade is done, one can't switch back to Hotmail anymore, and I can't see any improvement. I do have quite a fast CPU and enough Memory, but Outlook runs
very slow and I'm missing features!
Most I'm missing the ability to reply to messages in junk-mail and I can't switch between connected accounts when using the mobile version on my Android Tab.
I suggest, before losing many users, you (MSN) first work on making Outlook.com as convenient as Hotmail was, and meanwhile give us the possibility to switch back to Hotmail until everything is fixed!
Best Regards
Chris