Athenahealth ( ATHN) coverage initiated at Goldman Sachs with a Neutral rating, due to valuation. See differentiated business model and competitive advantages, however shares trade at a significant premium to all relevant groups on various metrics. Price target at $41. Athenahealth initiated at Jefferies with Buy rating. Price target starts at $46 with 2008 eps estimates set at $0.49. Acuity Brands ( AYI) upgraded at Baird from Neutral to Outperform. $56 price target. Despite slowing US outlook, management has a solid track record of maintaining growth and profitability. FormFactor ( FORM) upgraded at Citigroup from Hold to Buy. $44 price target. Downside appears limited, as the stock has pulled back to an attractive level ahead of what should be a strong 2008. General Motors ( GM) upgraded at UBS to Buy rating from Sell. Price target jumps to $48 from $24 while FY2008 eps estimates hold at $2.25. Nexen ( NXY) upgraded at FBR to an Outperform rating due to stock underperformance relative to rise in crude oil. Office Depot ( ODP) downgraded at Deutsche Bank a Hold rating due to restatement announcement. Pacific Capital Bancorp ( PCBC) downgraded at KBW from Outperform to Market Perform. Bank warned for the second time this year, and investors are unlikely to be rewarded in the near term. Petro Canada ( PCZ) upgraded at FBR to an Outperform rating due to weak stock price performance relative to rise in crude oil.