ComScore issued its latest report on smartphone usage in the United States for the three months ending January 2010. Google moved up significantly, while Palm dropped a few (more) percentage points. RIM, however, remains champion.ComScore looked at those using cell phones aged 13 and over in the U.S. There are 234 million such subscribers. Research In Motion saw a small bit of growth, swelling from 41.3% of smartphone users to 43.0%. Apple's presence grew less, climbing from 24.8% to 25.1%. Microsoft was the biggest loser, and saw its share erode from 19.7% to 15.7%. (Keep in mind, Microsoft introduced Windows Mobile 6.5 in October 2009.) Google jumped up from 2.8% to 7.1%. Last, Palm dropped from 7.8% to 5.7%, hitting last place in the U.S. market (not counting Nokia's S60).

RIM's hold-steady position isn't too surprising. The company debuted a few new handsets during the October - January time frame, including the Bold 9700 with both AT&T and T-Mobile, and the Storm2 on Verizon Wireless.

Apple's moderate increase in market share is more troubling. Sure, it still climbed, but the growth rate slowed way down. Has the iPhone reached its peak in terms of user adoption?

Microsoft's precipitous drop in market should be most troubling. The company debuted the newest version of its mobile operating system during the three months comScore collected data. The problem? Window Mobile 6.5 launched with weak reviews -- and rumors of Microsoft's Project Pink and Zune phones were already well and alive.

Google's increase in market share seems to be wholly based on the introduction of the Motorola Droid, which launched in November. Android handsets became much more widely available in the last quarter of 2009, with the HTC Hero and Eris; Samsung Behold II; Motorola Droid; and a couple of others. Can Google's numbers keep growing, however? Weak efforts from Motorola, such as the Devour and Backflip put a stain on Google's otherwise clean record.

Last up, poor Palm. It lost 2.1 percentage points and fell to 5.7% of the market. Palm introduced a new model in this time frame, the Pixi, its second webOS device. If anything, Palm should have seen a slight increase in share. That webOS has failed to help the company regain market share is bad news indeed. In recent weeks, both Spring and Verizon Wireless have dropped the price points of webOS devices in order to encourage sales.

How will the rankings change for the next three months? Anyone want to guess? I'd suggest that Microsoft and Palm will continue to lose, while Google and (to a lesser extent) Apple gain. Given the wide gulf between iPhone adoption and RIM's installed base, I'd say it has nothing to worry about. At least until iPhone OS 4.0 is announced.