R.A. Dickey was optioned to Triple A Rochester to make room on the 25-man roster; Boof Bonser was moved to the 60-day DL to clear space on the 40-man roster. News story on the moves here.
Pavano's career has been a real roller coaster. As a minor leaguer he was part of the package the Expos got for Pedro Martinez. While with Montreal, he gave up Mark McGwire's 70th home run of the 1998 season. He was one of the rotation anchors for Florida's 2003 World Series champs, won 18 games for the Marlins in 2004, then signed a big contract with the Yankees, for whom he barely pitched (2005-2008, a total of 145 2/3 innings). One of the tabs called him "American Idle."
With Cleveland this year: 9-8 (for a 46-62 team) with a 5.37 ERA — and, on the plus side, 6.3 strikeouts per 9 innings and 3.83 strikeouts per walk.
He's not a great pitcher, but he gives the Twins a reasonable alternative to trotting Francisco Liriano or Glen Perkins out every fifth game. My guess is that Liriano is more on the edge of losing his rotation spot than Perkins is.