We received the new Nintendo Power at work today and it contained a review for Sonic and the Black Knight.
The game scored an 8.0. They mention that you can pretty much run through the game in a day, but that there is a LOT of optional stuff you can do: gain more followers, gain level in three fighting styles, optional quests, run through the game with the other three optional characters, gain more equips, interact with villagers, etc etc.
They also mention the controls and stage designs are pretty smooth but there were a few times where swords strike didn't chain well and would leave you vulnerable to a counter attack. You can usually just slash and keep running but clusters of enemies and bosses recquire you to slow down (though with clusters you can try to just jump over them and forget about the survivors). Like mentionned above there's three sword style and you can parry and block attacks when you slow down.
Looks at the very least rental worthy.