Thin is clearly in at Samsung. The company's new BlackJack i607 from Cingular is the spitting image of Verizon's Motorola Q, also black, and one of the thinnest phones you can buy. Though the two PDA phones look alike, the BlackJack features a lighter, narrower design and more-robust multimedia capabilities (such as streaming music and video).

The BlackJack is 4.4 inches tall, 2.3 inches wide, and 0.5 inches thick (the Q measures 4.6 by 2.6 by 0.45 inches). It's also incredibly light at 3.5 ounces, compared with the Q's 4.1-ounce weight. While I like the BlackJack's compact size, thumb-typing on its QWERTY keyboard feels cramped. (The Q's keyboard has blank space at the bottom where I can rest my thumbs, making typing easier.) The BlackJack's tactile keys are a pleasure to use, though.

The thumbwheel on the right side moves swiftly and makes navigation manageable; pressing and holding it brings up the Quick Launcher window, which lets you jump to your calendar, to music, or to a Web page. (You can change which apps appear in the window.)

Among the BlackJack's major selling points are multimedia features that other PDA phones in this class lack. Through Cingular Music, it will stream 25 channels of XM satellite radio (for $9 a month), and it supports subscription music services such as eMusic, Napster, and Yahoo. It will also stream video content from CNN, HBO, and others (fees vary). One disappointment, though: Cingular doesn't offer an over-the-air music download service. You can transfer songs from your PC and then store them in the BlackJack's meager 64MB of RAM, but you're better off buying a microSD card for music, video, photo, and other file storage.

This model also offers stellar messaging capabilities. Running the Windows Mobile 5 Smartphone Edition OS, the handset includes Internet Explorer, syncs Outlook e-mail, and supports push-based e-mail delivery via Microsoft Direct Push, Good Mobile Messaging, or Cingular XpressMail. You can also sync POP3, IMAP, and SMTP e-mail clients. You can stay in touch through instant messaging (AIM, MSN, and Yahoo) as well. Though you don't get a mobile version of Microsoft Office with the operating system, you can view Word documents, PDFs, Excel sheets, and PowerPoint presentations through the included Picsel Viewer program. And like many PDA phones, the BlackJack includes a calendar, a notepad, voice notes, and a metric and currency converter. In my experience, though, opening and closing some apps, backtracking to a previous Web page, and using the 1.3-megapixel camera were sluggish operations, the phone typically requiring 1 to 2 seconds to process the commands.

In my trials, call quality generally sounded fine on both ends. The speakerphone worked okay, too. On my end the phone's speakers produced fairly crisp audio, but a few of my callers had a hard time hearing me and said they noticed an echo. Talking around noisy or windy environments isn't advisable, either, as the phone picks up a lot of background sounds.

Its battery life in our lab test was good: It lasted 6 hours, 21 minutes--more than 40 minutes longer than the Motorola Q, but far short of front-runners like Cingular's 8125, T-Mobile's Dash, and RIM's BlackBerry 8700g. The package comes with a spare battery and an external charger. You can also charge the battery while the phone is plugged into a PC via the included USB cable.

A minor quibble: In all applications except streaming-video mode, you have to use the thumbwheel instead of the volume control on the left side to adjust volume. (What finally tipped me off was a little speaker icon on the screen with a percentage number next to it--100 percent means it's at the maximum level.) Dialing a number on the BlackJack was a little challenging. The numbers are inconveniently placed between nonnumeric keys, so I often pressed a letter by mistake when I should have pressed the adjacent number. I later discovered that when I pressed the letter to the right of a number, it entered that number. For example, pressing the letter R (which is located to the right of the number 1) enters the number 1.

Signal strength and data performance varied quite a bit in my test area of San Francisco and a few surrounding suburbs. Within range of Cingular's HSDPA 3G network, streaming video from HBO, for example, was smooth. On the EDGE network, though, the graphics often looked blocky, like a David Hockney photograph. Web pages usually loaded within 15 to 20 seconds, though they sometimes took longer. Cingular's HSDPA network is available in many cities where the carrier does business; in these spots, having Wi-Fi would have been nice, but alas, the BlackJack doesn't provide it.

At $300 (with a two-year contract from Cingular), the BlackJack costs $100 more than the Motorola Q. For that extra amount, you get streaming-media capability, a second battery, and a very light and compact design. The lack of Wi-Fi may be a deal breaker for some users, but if you're in the market for a PDA phone, the BlackJack is a winning hand.

-- Grace Aquino