In its three years, the iPhone has redefined the mobile device. But despite the iPhone's popularity, it is by no means certain to become the mobile equivalent of Windows, the dominant platform that defines our experience of a particular technology, as well as the business choices that surround it.

Google's Android 2.0 OS is the latest in a series of mobile offerings seeking to derail the iPhone's momentum. Backed by heavyweights Google, Motorola, Verizon Wireless, Acer, and other big-name manufacturers, Android could potentially knock the iPhone down a peg. After all, while users love the iPhone, Apple's controlling tendencies have frustrated developers, and its disrespect for business concerns have frustrated IT.

[ InfoWorld's Neil McAllister wonders why Android developers seem so unhappy. | Get InfoWorld's 20-page hands-on look at the new generation of mobile devices. | Video preview: See the Android 2.0 Droid in action. ]

Meanwhile, Research in Motion's BlackBerry remains well entrenched, despite the iPhone onslaught and RIM's own slow response in adapting the BlackBerry beyond messaging. And for most of the world, Nokia's Symbian is king -- not to mention the fact that Palm and Microsoft have yet to give up on their respective WebOS and Windows Mobile visions.

Simply put, it's a tumultuous and rapidly evolving time for mobile -- so what's a buyer, IT organization, or developer to do? Here's a guide to the key issues that are shaping the still young mobile marketplace, and how Android will fare carving a niche for itself in mobile IT.

Motorola and Verizon: Sights are set on the iPhone
In a few weeks, the first smartphones using Google's Android 2.0 will be available, with iPhone competitors Motorola and Verizon Wireless already promoting Droid as the iPhone killer. And no doubt, the recently released Android 2.0 SDK will draw developer interest. But we've heard this song before, hype and SDK, applied both to poorly designed products such as the RIM BlackBerry Storm as well as to good products such as the Palm Pre. None, including Android's previous incarnations, has succeeded in unseating the iPhone.

So what makes Android 2.0 a plausible competitor? For starters, this fourth version of the Android OS finally supports Microsoft Exchange, though carriers and device makers are able to turn off that feature if they want. It also supports multiple e-mail accounts in a single inbox. Increased support for HTML 5 technologies -- including database APIs, offline application caching, and geolocation -- also mean that Android 2.0 devices and apps can have the kind of rich functionality the iPhone is known for, in a multi-app context unknown to the iPhone.

Of course, the Palm Pre's WebOS also offers most of these capabilities, yet has not stood up to the iPhone. However, that may be more an issue of Palm being a small company at the edge of extinction before the Pre came out and the fact that only an also-ran carrier widely rumored to be up for sale -- Sprint -- agreed to offer it in the United States.