Yes, it's really rather surprising that it doesn't work with a lot of accessories. I think pretty much everything that will charge an iPod will charge an iPhone, but the speakers don't seem to work, even if you turn off the iPhone's cell phone radio.
My Apple wired radio remote also doesn't work, which is a disappointment. At least the iPhone ear phones allow you to pause and advance songs, but I like to be able to control the volume of my songs without taking the device out of my pocket.