I'm coming around to thinking that the Apple one -- overpriced as it is (and does NOT come with a cable!) -- is the only way to go. I have a cheapo ebay one that doesn't work with iPhone: gives the "use airplane mode" popup, and sometimes won't sync right. I've also tried the Seido jr. dock. Every four or five times my PC says that the iPhone disconnected or timed out before syncing was finished. It somewhat corrupts the iPhone, in that I have to resync successfully again, or my non-Apple apps stop working (weird, I know). Sometimes when I plug the iPhone into the dock, it doesn't even recognize it.
I got the Seido dock because my iPhone has a case. What I've decided to do is just not use an insert/adapter with the Apple universal dock (I have the Apple iPhone-specific dock, but that absolutely requires no case), so that the iPhone w/case fits no problem. At the very least, that's what works with the Griffin charger (non-sync) dock, and the various Bose SoundDocks we own.
I don't know why it's so hard to make a proper dock . . . .