Well I just installed it and have used it for 15 minutes. So far it's mostly just irritating me.
I set up IE6 so all the buttons I needed were installed on the very top along with the drop down menus. So I had more real estate for the web page. IE7 doesn't even have drop down menus, everything is a dumb button on the screen so you need them there taking up space. Now I lose about 10% of the real estate to this. The layout seems a bit "fad-like" to me. I'd like all my applications to look and act the same please, don't fuck with standards unless you are really improving something.
The favourites is also annoying. Before yould easily browse your subfolders without clicking anything, now you have to go and click each folder to see what is in it. That's just idiotic non-ergonomic design.
The tabs are a nice change to avoid task bar pollution. However, they work inconsistently, web sites that are designed to open new windows still do so instead of opening a new tab.
One of the web sites I view was also rendered all messed up. Could be IE6 was just making it look right out of dumb luck though.
Perhaps messing around with configurations I can change IE7 to be happy with it but so far it seems like a step back and if I'd known I probably would have stuck with IE6. Oh well you have to move with it or it will leave you behind I guess.