Benzinga's Top Upgrade Summary Since Market-Open for May 18, 2012

Listed below are today's Top Upgrades at Benzinga since market open:FBN Securities Upgrades Aruba Networks (NASDAQ: ARUN) to Outperform:FBN Securities comments, "We are upgrading shares of ARUN from Sector Perform to Outperform and lower our PT from $24 to $18. As we publish this note, shares are trading near $14, which we see as a good entry point. The stock has declined about 30% over the past month, it is still guiding for revenue growth of about 20% (~27% adjusted for the lower China service provider business than a year ago) in FQ4, it has~ $3 of net cash/share (~20% of the stock price), and opex leverage continues (opex% is now 52% vs. 55% a year ago). On the negative side, the company's momentum, like others in the networking industry, has slowed, while its growth premium over CSCO declined from 26% a year ago to only 4%."Stifel Nicolaus Upgrades Marten Transport (NASDAQ: MRTN) to Buy:Stifel Nicolaus notes, "Marten Transport is one of the largest temperature-controlled truckload-based carriers in the U.S. and hauls freight such as food, pharmaceuticals, and cosmetics - all of which tend to hold up well even as the economy experiences soft patches. We believe that the company should be able to further leverage its maturing regional truckload, intermodal, and brokerage businesses in 2012, 2013 and 2014 as shippers of perishable goods seek to align themselves with large, financially strong, and well systematized carriers as they anticipate accelerating tightness in supply and demand within the temperature-controlled arena. We believe Marten Transport is one of a few large temperature-controlled carriers (and the only publicly traded temperature-controlled carrier) that should benefit from those trends."Stifel Nicolaus Upgrades Hub Group (NASDAQ: HUBG) to Buy:Stifel Nicolaus comments, "We are upgrading the common shares of Hub Group, Inc. from Hold to Buy primarily due to valuation. Our 12-month target price for HUBG is $41 (or 15.5x our 2014 EPS estimate of $2.65), which provides over 23% upside relative to the most recent closing price."Miller Tabak Upgrades Sirius XM Radio (NASDAQ: SIRI) to Buy:Miller Tabak writes, "We are upgrading our recommendation on Sirius XM Radio (SIRI-$1.89-Buy- Target $2.55) to Buy from Neutral and keeping our target at $2.55/sh. We believe the selling has been overdone related to the evaporation of hopes for a SIRI stock buyback program (which would help creep up Liberty Media's (LMCA-$80.66-Buy-Target $101) ownership. It was perhaps the LMCA lack of success in petitioning the FCC for de facto control of SIRI licenses (which is still in an appeal process) that precipitated LMCA's forward purchase contract that, if physically closed in 3Q12, would increase its ownership to 45.2%. We still believe a logical ultimate step could be eventual control by LMCA and/or a reverse Morris Trust for LMCA shareholders that could result in FCF being used for share buybacks."FIG Partners Upgrades First Midwest Bancorp (NASDAQ: FMBI) to Outperform:FIG Partners went on to say “Given FMBI's comments on the 1Q12 conference call regarding NCOs/credit we are not really that surprised by the recent pullback. That said we now believe those comments have been mostly reflected in the shares. Accordingly with FMBI shares now trading near the $10 level we believe the risk/reward is more favorable for investors looking to get “long” FMBI shares.”All of Benzinga's Analyst Ratings news can be viewed here.