In a blink of mere months, the mobile "smart" phone has been transformed from a pricey corporate gadget to an affordable alternative for ordinary folk.

In the last month alone, Cingular Wireless has unveiled three devices priced as low as $200 (after jumping through the assorted contractual hoops and rebates).

That's well below the $300 to $500 that BlackBerries, Treos and Pocket PCs have generally fetched, even with promotional savings.

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The shift began in May with the "Q" from Motorola Inc. (MOT), a slender handset with a full QWERTY keyboard for typing e-mail that Verizon Wireless introduced for $200 and now sells for as low as $100 — a price cut that happens to coincide with an increasingly crowded field of rivals vying for consumer dollars.

T-Mobile struck twice over the summer with the launch of the Pearl, the first BlackBerry with a camera and music features, and a hybrid cellular and Wi-Fi device called the Dash. Both were priced as low as $200, though the Dash can now be had for $150.

But no carrier has gone as wild with consumer-friendlier smart phones than Cingular, which has rolled out four such devices since September. I tried out three of them: the Nokia E62, the Samsung BlackJack and the Palm Treo 680.

Given today's wide selection, and how limited the choices were just a year ago, it's mildly absurd to complain about any of these devices, all of which make the "hot" smart phones of yester-Christmas look clunky, pricey and primitive. That said, they all have plenty of deficiencies.

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Samsung BlackJack

The BlackJack is easily a standout among the three devices, if only because it is compatible with Cingular's new high-speed wireless Internet network, available in 145 markets and growing. It's also impressively small — less than a half-inch thick, 2.32 inches wide and 4.45 inches tall — and weighs 3.5 ounces.

Another plus, somewhat surprising, is that there are two different ways to navigate the menus.

On the front, there's a four-directional circle below the screen with a button in the middle to click, as well as dedicated "back" and "home" buttons alongside.

Alternatively, borrowing from the BlackBerry playbook, there's a thumb wheel and back button on the right side of the device to scroll and click through menus.

Despite the size constraints, the phone features a slot for removable memory to store music and photos, as well as a 1.3 megapixel camera. One notable omission, as with nearly all Cingular phones, is GPS satellite capability for location-tracking applications.

The BlackJack runs on Microsoft Corp.'s (MSFT) Windows Mobile platform, a plus and minus.

The familiar look and feel of Windows will hold some allure for newcomers to smart phones. But the mobile version of Microsoft's computer operating system suffers flaws, as do the Windows applications that ride on it: frozen screens and cumbersome menu design, to name a couple.

When trying out Cingular's video service, for example, the downloads were far speedier over the next-generation network as compared with the faucet-drip pace of most wireless devices.

But watching the videos was another matter. I downloaded an episode of "Curb Your Enthusiasm" from the HBO Mobile premium service, which at $5 a month isn't the sort of bargain that would make you especially patient about poor quality.

Perhaps it was Windows Mobile or the Windows Media Player, but Larry David's face kept freezing up on the screen.

Another annoyance, not unique to Mobile Windows, is that it's difficult to switch from one application to another — let's say, checking your e-mail between episodes of "Curb Your Enthusiasm" — without starting over each time.

Also, while Windows Mobile runs e-mail applications such as Good Mobile Messaging and Microsoft Direct Push, the most popular one of all is missing, as Microsoft and BlackBerry provider Research In Motion Ltd. (RIMM) have not yet figured out how to play nicely together.

Typing e-mails and text messages on the keyboard was pretty smooth, though I suspect some with larger fingers would be more comfortable with the bigger keys on a wider device.

Despite a gray shading to distinguish the keys featuring both numerals and letters, I found it hard to find the right buttons to dial a phone number.

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Nokia E62

The E62 is the first mass-market smart phone in the United States running on Symbian, a mobile operating system that's far more common than Palm, Windows or BlackBerry everywhere but North America.

I'd say we're better off on this side of the pond. The Symbian OS stuttered and paused with every click, and the menus of Nokia's user interface were littered with programming jargon, forcing constant trips to the manual.

One advantage with Symbian, though, is that it's compatible with just about every major e-mail platform, including BlackBerry's and Microsoft's, as well as Good and Nokia's Intellisync.

The device itself struck me as very comfortable to hold, the keys as spacious for typing as any BlackBerry, though a colleague found it large and cumbersome for smaller hands.

One common design complaint: When gripping the handset, we kept accidentally hitting a side button designed for quick recording of voice memos and voice-activated commands.

The screen was big, measuring nearly 3 inches diagonally, or about a third larger than BlackJack's. Other features include a memory slot. One major bummer: no camera.

The flipside of the larger screen and keys, of course, is that the E62 isn't as small as its newest rivals. It weighs 5.1 ounces, which is slightly lighter than the new Treo, but heavier than BlackBerry, BlackJack and Q. The E62 measures 4.6 inches top to bottom, 2.7 inches across and a little more than a half-inch thick.

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Palm Treo 680

I've never been a huge fan of the Palm (PALM) operating system or the Treo, finding its size too bulky, its keys and functions clunky. But I do know enough people who so love their Treos that I attribute some of my opinions to lack of familiarity.

One thing's for sure: where the $400 and $500 premium the Treo has always commanded made it a non-starter for most everyday users, the Treo 680 is well within reach for the masses at $200, with strings attached.

Palm also has done a nice job slimming the Treo some: At 5.5 ounces, the 680 weighs nearly an ounce less than other Treos.

It's almost identical in dimensions, except that with the 680, Palm has eliminated the nubby antenna that juts out from the top of other Treos.

On the downside, the resolution of the 680 camera is just a quarter of the 1.3 megapixels on the Treo 700. The Treo 680 also lacks compatibility with the speedier Cingular network.

Both omissions are a sure sign of the difficult tradeoffs Palm faced in trying to bring down component costs without too many sacrifices.

Notably, one sacrifice not made is the Treo touch screen, giving the 680 at least one feature that no other similarly priced smart phone can boast.