I've been a big tablet PC fan for years. I still prefer using my tablet, in portrait mode, to browse the web over any other device. Apple have even begun to show the mainstream users that the tablet form factor can be useful.
So why do the IE team seem to have missed this. Moving the favourites/home/menu buttons to the right hand side of the screen makes it incredibly uncomfortable to access for such a common need, as your arm naturally tends to favour the top left of the screen. Why do this? What do you gain? Likewise, the iffy supprt for pinning to the taskbar when it's anywhere but the bottom of the screen seems poor (most heavy tablet users soon learn the value of putting the taskbar at the top of the screen). Is this likely to improve post-beta?
And last, but by no means least, when I'm browsing in portrait mode vertical space is in abundance and horizontal space is at a premium. Yet IE9 still insists on trying to cram everything onto a single row, making the address bar useless (I'm lucky if I can see https://) and giving me barely room for a couple of tabs. If you don't want to make tabs on a new row optional, at least could you consider laying out differently on a portrait display?