According to a May comScore survey of 35,520 U.S. mobile subscribers, almost 30 million Americans now own a smartphone. With expectations of skyrocketing smartphone sales, it's worth checking which OS platforms are gaining steam. This list, which compares May smartphone OS statistics with those from February, does not reflect the introduction of the Palm Pre or the iPhone 3GS--but don't worry, FierceWireless will publish those updated numbers when they become available. Slideshow