Earlier this year, Blue announced the second revision of the Mikey, with enhanced features for $20 more than the first $79 version. That's the one we used, and it looked and worked great. They've added a line input (for recording guitars), and a USB passthrough, as well as put the entire body on a swivel (so it can even swing all the way around and point forward while shooting video on the 3G.
Construction is quite solid, as with all of the Blue mics, and the sound is terrific -- we held the mic at about chest level while recording, just randomly pointed in the air away from us, and the played-back audio, even on a crowded convention floor, sounded as if we were speaking directly into a studio microphone. Blue also played back a full band recording for us that had been done with the Mikey, and while the mix wasn't perfect (it never will be when you're recording a full band with just one microphone), you could hear both the highs of the cymbals and the lows of the bass and the kickdrum as the jazz band played. It's not the best mic ever, but for a microphone this portable that's recording into an iPhone, it sounded very impressive.
The new Mikey is a solid mic -- you will not find a better iPhone microphone for $99 guaranteed, and the sound actually rivals some higher end mics designed for standard recording. Blue hasn't disappointed yet -- if you need a worthwhile microphone but don't want to carry a lot of recording gear, it's worth a look if not a purchase when it releases later this year.