Slacker's free-DJ-in-your-pocket service is back, this time with a new—and much smaller—portable player. The G2 syncs up beautifully with your personalized Slacker music stations over Wi-Fi, and it sounds great to boot, although filling the G2 with tunes requires some patience.

Measuring 3.4 by 0.5 by 2.1 inches and weighing in at about 2.6 ounces, the flash-based Slacker G2 (4GB for $199, 8GB for $249) is considerably bigger than, say, the new, 4G iPod Nano or Microsoft's flash Zune players. That said, the G2 is much smaller than the original Slacker player (which I checked out back in January at CES), and it has a killer feature that the iPods and Zunes lack: access to Slacker's free music service, which lets you sync up customized channels (or "stations," as Slacker calls them) of free tunes (from both major labels and indies).

Syncing up the G2 is easy; just plug your G2's ID number into your Web-based Slacker account, then connect the G2 to any open Wi-Fi network. Once connected, the G2 will automatically start downloading your Slacker stations—pretty simple, although filling the G2 can be a lengthy process (about two hours in my case). I'm betting most users will prefer to sync their G2s overnight to avoid the wait. [Update: The transfers go much faster on subsequent syncs.]

Playback on the G2 is pretty impressive; you get album art on the 2.5-inch, 320 by 240-pixel TFT display, and a BlackBerry-like jogdial along the right side for navigating the player's various menus. Just above the screen are "favorite" and "ban" buttons; click one or the other while you're listening to fine-tune your music preferences (just as you can with the Web-based Slacker player).

Also nice: The wealth of artist and album info that you can browse while listening to your tunes. Just click an artist name for pictures and a lengthy bio, or select the album art for a full review. Apple, take note.

Of course, all that free music comes with a couple of strings attached—specifically, you can only skip six songs an hour (the same limitation you'll find on the Slacker Web player), and you may also start hearing advertisements (about one an hour) starting next year. That's actually not so bad, considering all the free tunes you get—and besides, if you want unlimited skips, you can always cough up $7.50 a month for "premium" Slacker service. Want to hear your own music? PC users can transfer MP3s to the G2 via the included USB cable. (No MP3 transfers for Mac users, unfortunately.)

Sound quality on the G2 was pretty good to my (untrained) ears, and the included earbuds are certainly above par (if a bit tinny). There's also a 10-preset equalizer for tweaking the sound, along with a volume "normalizer" that'll keep sound levels relatively steady.

Overall, the G2 makes for a worthy successor to the original Slacker Portable Player, and it’s a tempting choice for adventurous music lovers looking to discover new tunes. That said, I'd advise Slacker newbies to try the Web-based service first—clever though it is, Slacker isn't for everyone. Also, if you're a BlackBerry user, consider waiting until Slacker's free BlackBerry app goes live next month; you'll get most of the G2's functionality, minus the extra hardware.