I'm not sure why you think it's clunky, it's fairly small and light, fits easily in one hand, has good ergonomics, and looks good too. If you are thinking of using smartphone app most of the time, then the Ultimate might not be for you, because the Ultimate is made to be your primary interface.
The software brought in my activities from my 890 just fine, for the most part. I had to tweak some activities and that was about it. It will likely bring in all yours too, but if you have a lot of customizations then you can expect to have to do some work, but not a lot.
Lots of remotes include the four colored buttons now, and so the Ultimate has those also. On the touchscreen you can put any buttons you want, so it'd make more sense if you gave those actual names instead of red, green, etc.
I don't see how the IR mini blasters will help you control devices in other rooms. Those have to be plugged into the hub. I'm sure you could set up the remote to control various TVs with it's IR capabilities, but then you'd have to take the remote room to room.
I can't speak to the maximum number of devices, I'm only using about 8 myself.