When it comes to iPhone compatibility with old-school docks and accessories, the fear factor has been pretty high. Compounding that is the annoying message you get as soon as you dock an iPhone: "This accessory is not made to work with iPhone." Then, more mysteriously, "Would you like to turn on Airplane Mode to reduce audio interference (you will not be able to make or receive calls)?" I have tested it on a few music docks, daringly answering "No" each time, and I'm happy to report, it's no big deal. On the flipside, anyone who bought one of those newer video docks is bound to be frustrated, because in our testing, they didn't work. There are two kinds of docks: ones that let you control music from the iPod itself and ones that take control of the iPod, like BMW's notorious first dock and many subsequent (and more affordable) accessories since. The Bose SoundDock is an example of the former; the DLO HomeDock and Harman Kardon's Bridge dock are examples of the latter.
Regardless of the dock type, regardless of whether the iPhone is set for ring or vibrate, here's what happens: you are rocking out to your music when it suddenly—though gracefully—fades out. If it's on ring, you hear the one of the cheesy Apple ringtones, but it doesn't play through the system, it plays through the iPhone speaker. (If it's vibe, you may not hear anything.) You can even answer in-dock, and tap the speaker button to put the call on speakerphone. The instant you hang up, your music fades back in, no problem.
The video dock, on the other hand, was a total bust. Mind you, I only tried one, the Memorex iFlip, but the prospects are grim. Since iPhone doesn't have the video options screen that a video iPod does, you can't choose to route the video out. Since it would never play video internally and externally at the same time, it seems video is doomed to stay in the iPhone forever. And that "audio interference" Apple mentioned, well, the iFlip is the first time we heard it. A low, digitally unpleasant moan. More updates on that subject soon.
This is mixed news for every iPhone aspirant who has spend hundreds on iPod docks and accessories, but still it's not a comprehensive, scientific study. We will continue to test and report back to you as we learn more.