The earlier M602 includes a USB port that lets you to sync your iPod with iTunes on your Windows or Mac machine. That's missing in this model. Also gone is the video output (you know, the little yellow jack you're used to seeing on TVs) that gives you the option of displaying your iPod and iPhone videos on a TV. A small wireless remote is included, but it offers limited functionality--you can skip tracks forward and back, pause and play, and adjust the volume and bass/treble levels. Navigating through the menus on your iPod/iPhone is not possible, though.
As for the Altec Lansing T612's sound quality, it seemed very similar to the quality of the M602--which is to say, decent. Like a lot of these all-in-one speaker systems, this model has very little in the way of stereo separation. The speakers, which are equipped with two 3-inch drivers and two tweeters, are essentially next to each other; as a result, the system probably sounds best if you're sitting only about four feet away from it.
The treble and midrange are the system's strongest suit, with voices, guitars, and acoustic music sounding quite pleasant. As with the M602, the Neville Brothers and the Burt Bacharach/Posies sounded good, with bass performance delivering a noticeable step-up from similarly sized systems. The low-end held together at higher volumes better than we thought it would on bass-heavy tunes such as Prince's "Incense and Candles" on his 3121 album. Toni Braxton's "He Wasn't Man Enough For Me" and Amy Winehouse's "Rehab" also delivered decent punch. That said, we had to wind down the bass a bit to avoid distortion on an Art of Noise tune--though it still played loud enough to fill a small room.
The mobile phone anti-interference technology worked as advertised. We connected an iPhone and didn't hear any audible hiss or buzzing. (The iPhone will work in most other iPod speaker docks, but you need to switch it to airplane mode to avoid the resulting interference--which would in turn send all your incoming calls straight to voice mail.) We called the phone while we were listening to music, and the music automatically turned off when the call came in. We answered the phone while it was still in the dock and hit the speakerphone button to talk. Alas, no sound came through the T612's speakers, only through the iPhone's speaker. But we were able to talk just fine on the phone while standing at close range. Then, after we hung up the call, the song we were listening to resumed. True, that's a feature of the iPhone, not the dock, but it was still pretty nifty.
In the end, we really didn't have any major complaints to report--except that we wish Altec Lansing had kept some of the features previously available in its earlier M602. It's too bad the video output's missing, and it also would have been nice if a good old-fashioned FM radio was on board. But clearly the T612's iPhone-centric features are its main selling points. So those who don't have--or aren't planning to buy--an iPhone will probably be better served by one of the many other worthwhile iPod speakers on the market. But for those who have an iPhone (and maybe even an iPod or two), the T612 is worth considering, particularly as the street price drops to below $150. It may take a little while, but if the price of the M602 is any indication, there's room for some discounts.