Has anyone else gone for this, when you sign into hotmail there should be a link saying cllick here for BETA and thats more or less it and your on BETA.
Its sweet, instead of loading the page everytime you want to see a new message theres a list at the side of your inbox etc. and whats in it and when you click on one th message pops up on the right... No loading what so ever Its great.
It also has a built in spell check that comes in handy for formal messages and tells you if theres something wrong.
Personally i think its great although there may be a few bugs because 1 Its a BETA and 2 so far its only fully supported for IE but i aint noticed a bug in FF yet.