(Ford story updated with Ford April sales figures, analyst reaction to the figures and stock price movement.)

Ford ( F) is still generating a mixed bag of reviews after reporting strong first quarter earnings last week and yet another month of sales improvements this week.

Ford Fiesta

The reaction has hardly surprised Ford equity analysts.

"Ford has had a strong run over the past year, so it's not surprising people have locked in profits," Standard & Poor's analyst Efraim Levy told TheStreet. Now "the question is, what will you do for me next?" Meanwhile, Craig-Hallum Capital analyst Steve Dyer said that "it's natural that people would begin to question how much upside is left."

Excluding items, Ford on April 27 posted first-quarter earnings of 46 cents a share, exceeding the 31 cents a share forecast by analysts surveyed by Thomson Reuters.

The next day, Credit Suisse analysts downgraded Ford to underperform from neutral. "We do not think this level of profitability is sustainable," analyst Christopher Ceraso wrote in an investor note. He sees "profit headwinds on the horizon," citing a list of concerns including "rising structural costs, to support global expansion; rising raw material costs; rising incentive costs in the U.S. and Europe; and declining profitability in the finance company."

These headwinds may not be close enough to be seen just yet, but Ceraso predicts that they will show themselves later into the year.

On May 3, Ford reported a 25% increase in April sales, the fifth straight month Ford sales have increased more than 20%.

S&P analyst Efraim Levy said he thinks this is good enough to gain market share, "but we think a slow down from March's 43% is something to watch." He expects to see year-over-year improvement in new light vehicle sales to continue for the rest of the year, but thinks that some monthly comparisons will become more difficult.

Ford stock is up 2.1% at $13.29 in Tuesday trading.

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