The themes thus far are pretty buggy as a result of bugs in the first BETA of Theme Builder 6.0.
Personally I'd suggest waiting for a new version of Theme Builder that fixes these bugs - otherwise know that the themes you may find right now are probably a little quirky.
Yea..there's a really nice HTC SensuUI Theme that just rolled out last night. Works pretty good so far, although to take full advantage one needs Quicklaunch. The only thing is there is no Today calendar available yet because the Themebuilder is still in Beta