I'd guess it also depends on how diverse your library is and how specific your genres are, amongst a few other variables (I'm not sure exactly what Radio uses to choose songs). For me, I use broad genres with more specific styles tags (so I've got 8000 songs genre-tagged as rock, another 8000 genre-tagged as electronic, etc) so I get a pretty broad variety from Radio. I actually tend to think that it's too broad a range of songs. I often make jumps from Slayer to Miles Davis, even after a good handful of skips n' plays.
I think one of the main issues with the static Radio algorithms that MC uses is that they're tuned to the way Matt and Jim tag their libraries. So it works well for them, and anyone who has a similar approach to tagging music, but for others it produces odd and/or undesirable results.
All that said, gappie's suggestion is a good one for your case. At least you've got the rest of MC's power to save you from its weak Radio function.
-JB