Microsoft Windows Live team completed the roll out of new Hotmail to all 350 million users worldwide, but users facing issues with it continue to be a hot topic on Hotmail support forums. Today a moderator revealed that "A hotfix is going out this week (should be complete by end of this week) which should resolve the problems customers are seeing with high contrast display mode (the workaround is to turn it off). Also this hotfix should resolve the Hotmail performance degradation that we saw when customers are running Messenger on the web (the workaround is to sign out of web messenger).
For some customers who're using a mobile broadband connection on their computer and experiencing errors when accessing their Hotmail. We've found the issue and are working on getting the fix created and rolled out soon."
The high contrast display mode issue is outlined here.