SenseUI is basically a skinned version of Android that looks pretty amazing. It's too bad the HTC Hero, HTC's third Android phone, is the only device it can be installed on (almost).
HTC CEO Peter Chou said that Sense UI will be available even on older devices, but it turns out that exciting statement wasn't quite what it seems.
Due to contractual obligations, HTC cannot push out this new UI on phones that have Google branding on them -- that pretty much rules out all the existing phones in the US. Canadians, on the other hand, may be able to use the new UI, as there is no Google branding on their Rogers handsets -- but I wouldn't hold my breath for this either.
To make users happy, it would be nice if Google removed the restrictions that make it impossible for HTC to distribute their new UI to handsets.
There are other ways to get a better interface though -- home replacements. aHome is one of the most popular, but there are several available in the Android Marketplace including Sweeter Home (lots of potential here!), dxTop, and Open Home. From what I can tell, these apps are currently only available in the US market.