i think this sport has a lot of potential. i don't know very much about it except that the bikes are much more practical than repliracers. they could sell quite a few w/ gas prices the way they are and a strong sport backing them up.
More practical? Depends on the kind of riding you do. Supermotos are indeed very, very practical in the city or on tight, twisty roads. But they are very impractical on the highway or over longer distances.
I have a DR-Z400S (in addition to a Daytona), but I haven't bothered to get supermoto wheels for it yet.