Honeycomb looks great. I agree that "designed for tablets" its good marketing. They can play the angle that the ipad was based on a phone OS & Honeycomb has been built for the ground up with tablets in mind.
My guess (or atleast what I hope) is that Google will announce Honeycomb for phones as well. They would share the same UI just with one designed for smaller screens in mind. Ideally the phone OS wouldn't need the dual core processing (so fragmentation doesn't kick in). And this way both tablets and phones share the same platform making it a bit easier for developers.
Provided el goog did not invent any new kind of wheel, I think it is quite safe to assume, that honeycomb "tablet edition" changes are geared to support those new additional screen layouts typical to the tablets.
Like currently developer can define several different layouts, for example one for portrait and one for landscape, screen form factor, docking state, night/day mode etc.
So, there will be additional modes for tablets. And additional UI controls utilizing those modes.
Then google will need to modify all the system apps, I think this makes the most of the honeycomb overhead. To do it properly it is by far not enough to "inflate" your present smartphone apps. Samsung already hacked this into the most of the apps shipped with galaxy tab.
It is actually quite boring if you look at it from the smartphone point of view. More like the new UI skin if at all.
