MOST NOTEWORTHY: P.F. Chang's, ViroPharma and CSX Corp were today's noteworthy upgrades:

• Jefferies upgraded shares of P.F. Chang's (NASDAQ: PFCB) to Buy from Hold to reflect the company's capital preservation focus, which they believe will drive a best-in-class free cash flow yield in 2009. Despite upgrading shares, Jefferies lowered their target price to $28 from $31.
  
• Thomas Weisel raised ViroPharma (NASDAQ: VPHM) to Overweight from Market Weight on valuation as they believe the sell-off on the Lev Pharmaceuticals (LEVP) acquisition is unwarranted. The firm raised their target price to $15 from $10.
  
• Merrill upgraded CSX Corp. (NYSE: CSX) to Buy from Neutral based on valuation and improved results.

OTHER UPGRADES:

• Borg-Warner (NYSE: BWA) was upgraded to Outperform from Neutral at Baird.
  
• Credit Suiise raised Walgreen (NYSE: WAG) to Outperform from Neutral.
  
• SunTrust upgraded Arena Resources (NYSE: ARD), Bill Barrett (NYSE: BBG) and Concho Resources (NYSE: CXO) to Buy from Neutral.