Madieu was producing reasonably well (mid DB2) in my leagues, including the game against TEN when he played very little.
His only poor game was against the Vikings, which was a passing/turnover fest and those tend to be hit or miss for a player like Williams. Otherwise he was 5-2-0 and 9-2-0 with an INT in his other two healthy games.
Madieu is in the mold of Bryan Scott/Marlin Jackson types. Experienced at CB in college, but with a skill set more likely to be successful at safety in the NFL. Capable of and plenty speedy enough to cover a slot WR, big enough to play safety. Williams has played all three secondary positions in his NFL career and more than held his own at each. He's proven to be a solid tackler and is almost always around the ball as he's used in blitzes (run and pass), and will roam in coverage (2 sacks, 2 FR, 3 INT, 11 PD in 2004). In my mind, his prior usage mirrors that of a Darren Sharper or Troy Polamalu, in that he fills some traditional SS roles from the FS position.
Pay attention to how the Bengals address the "SS" position in the offseason. Some of Madieu's role may change if the Bengals can find another Marvin type guy (speedy with some size) to fill that role. Kim Herring is there now; he'll be returning from a broken arm. If he ends up being the guy, Madieu will retain excellent value and may be a buy-low situation.
I haven't heard anything concerning about his shoulder injury, which usually means he's in line for a full recovery. But I'd watch to see that he's still willing to attack and wrap ballcarriers before I fully signed off on that.
Bottom line, I think Madieu will be a productive DB2 at minimum, and has a better than average chance at long term DB1 numbers. I might like him more than Eric Coleman, particularly if the Jets commit to a 3-4. Certainly if he can be acquired "cheaply" I'd be all over him.
As of late last season, in the leagues I don't own him in, one owner wanted a 2nd rounder minimum, the other wouldn't discuss him.