MOST NOTEWORTHY: STMicroelectronics, Biogen Idec, American Community Bank and Crosstex Energy were today's notable downgrades:

• Lehman downgraded STMicroelectronics (NYSE: STM) to Underweight from Overweight, as they expect the company to underperform its peers.
• UBS downgraded Biogen Idec Inc (NASDAQ: BIIB) to Sell from Neutral, citing valuation and their belief that there would be no significant premium if the company was bought.
• American Community Bancshares (NASDAQ: ACBA) was downgraded to Hold from Buy at Stifel, based on valuation.
• Goldman Sachs downgraded Crosstex Energy Inc (NASDAQ: XTXI) to Neutral from Buy, citing valuation.

OTHER DOWNGRADES:

• PepsiAmericas Inc (NYSE: PAS) was downgraded to Underweight from Neutral by HSBC.
  
• Amodcs Ltd (NYSE: DOX) was removed from the Conviction Buy List by Goldman Sachs.
  
• Citigroup assumed coverage of Tenneco Inc (NYSE: TEN) with a Sell from a Hold.
  
• Morgan Stanley downgraded LDK Solar (NYSE: LDK) to Equal Weight from Overweight.

MOST NOTEWORTHY: Some of today's notable upgrades were Apple Inc (AAPL), Comcast Corp (CMCSA) and Crosstex Energy LP (XTEX):

• Apple Inc (NASDAQ: AAPL) was upgraded to Overweight from Neutral at Prudential and raised their target to $105 from $100 after their checks indicated a late March launch of Leopard, which is sooner than expected. Prudential believes Leopard will serve as a catalyst for Mac sales.

• Matrix USA upgraded shares of Comcast Corp (NASDAQ: CMCSA) to Hold from Sell as they believe the successful roll out of "triple play" product offering is driving sales growth.

• Crosstex Energy LP (NASDAQ: XTEX) was upgraded to Neutral from Underperform at Credit Suisse based on valuation.

OTHER UPGRADES:

• Citigroup upgraded shares of Seagate Technology Holdings (NYSE: STX) to Buy from Hold on valuation as they believe Friday's sell-off on concerns that Apple will use NAND Flash rather than disk drives in the next-generation video iPod was overdone. Citigroup doubts Apple will broadly move to NAND flash this year.

• Jefferies upgraded shares of Universal Health Services Inc (NYSE: UHS) to Buy from Hold with a $67 target as they believe industry fundamentals are strong for behavioral health and the valuation is attractive at current levels.

• Brean Murray upgraded shares of Scientific Games Corp (NASDAQ: SGMS) to Hold from Sell. The firm does not expect Scientific Games to hit its 2008 guidance of $2.00, but recognizes the long-term growth prospects should begin to flow to the bottom line.

• Credit Suisse upgraded the Chicago Mercantile Exchange Holdings Inc (NYSE: CME) to Outperform from Neutral on valuation.

• Baird upgraded Thomas Properties Group (NASDAQ: TPGI) to Outperform from Neutral.

• Bear Stearns upgraded Group Danone ADS (NYSE: DA) to Outperform from Peer Perform.

Analyst summaries provided by TheFlyOnTheWall.com (subscription required).

MOST NOTEWORTHY: Today's more notable downgrades included Dell Inc (DELL), Deutsche Telekom ADS (DT) and the Nasdaq Stock Market Inc (NDAQ):

• Needham downgraded Dell inc (NASDAQ: DELL) to Hold from Buy after the Q4 results as they now believe the company is unlikely to outperform for "at least" several quarters. They considered Dell's notebook shipments to be the biggest disappointment in the quarter.

• Deutsche Telecom ADS (NYSE: DT) was cut to Sell from Neutral at Merrill Lynch.

• JP Morgan downgraded the Nasdaq Stock Market Inc (NASDAQ: NDAQ) to Neutral from Overweight following the company's price cuts as they feel the new prices negatively impact the U.S. cash equity business.

OTHER DOWNGRADES:

• Baird cut Xerium Technologies Inc (NYSE: XRM) to Underperform from Neutral, citing increased spending plans and pressure from the underlying paper market that raised dividend sustainability concerns.

• First Albany downgraded Hyperion Solutions Corp (NASDAQ: HYSL) to Neutral from Buy.
  

• Sanders Morris cut Crosstex Energy (NASDAQ: XTEX) to Hold from Buy. Raymond James downgraded shares of Crosstex to Market Perform from Outpeform.

• Bernstein downgraded TXU Corp (NYSE: TXU) to Market Perform from Outperform as the firm believe the current bid from Kohlberg Kravis Roberts and Texas Pacific Group will succeed.

• Merrill Lynch cut Altera Corp (NASDAQ: ALTR) to Neutral from Buy.

Analyst summaries provided by TheFlyOnTheWall.com (subscription required).

Although oil continues to take a pounding, trading below $58 a barrel, natural gas has bounced strongly over the past week, up 6% today alone. A number of leading newsletter advisors have been adding natural gas-related stocks to their buy lists in anticipation of a rebound.

The key signal for Adrian Day, editor of The Global Analyst, occurred last week when he saw select natural gas stocks hold up even while gas prices continued to slide. Seeing this divergence, he told his subscribers, "It's now time to buy."

His top pick in the sector is EOG Resources (NYSE: EOG), one of the largest independent gas exploration and production firm in North America. He considers the stock cheap at 10 times earnings and 6 times cash flow.