The new Microsoft Hotmail interface is HORRIBLE. I think they tried too hard to make everything in the interface click and draggable... which is aggravating to no end. I switched back to the classic Hotmail interface immediately.
I use Gmail, but I tried the new interface when it was called Windows Live Mail. Try as I could, I failed to find a reason why you needed drag and drop or horrible looking themes. Microsoft fails at cross-browser support.
Yeah I use it and think its great, always wanted an interface with preview pane I hated all that double clicking and stuff just to read some cr*p email that im not intrested in reading anyway lol.
Only problems I've had recently is the style sheet not loading properly so the page looks really rubbish with text links everywhere.
I find the new interface slows me down (not my computer) and takes longer to load than the classic version... also, is seems to do funny things in Firefox every once and a while... Just my $0.02