So the upgrade Microsoft recently forced from old hotmail.com to outlook.com has been pretty ok in my books. The interface is clean and pretty snappy performance wise.
One thing I have found that I dislike is the new auto-login to web messenger. I don't need to chat with people, this is my email interface.
Some people suggest blocking via hosts file, however that didn't seem very user friendly. I did however come across this solution which uses ad-block (or ad-block plus) and custom filters in Firefox and seems to work nicely. I didn't go to the step of customizing styles via stylish but I mostly use hotmail from large monitors where giving up 5% width isn't an issue.
Great Instructions - Disable Messenger auto-login on hotmail or outlook.com web mail interfaces