The Kodak ZX1 is a continuation of Kodak's line of HD handicams. It is capable of taking excellent quality HD video in 720p. There are a large range of these sorts of cameras on the market now, with the Kodak and the Flip MinoHD being the market leaders, I would say. I have used both, and shall compare their relative merits.
1. Quality of image
This is the one everyone will really care about. The new Kodak ZX1 does make a noticeable improvement over its Kodak predecessor, particularly in low light. Previous Kodak USB cameras were virtually unwatchable in anything less than full daylight. The ZX1 performs well in overcast conditions, and is watchable indoors, though there is a noticeable increase in noise. However, the Flip MinoHD wildly outperforms it, with far more detail, less noise and less streaking. In daylight, I'd say the Mino HD still has the slight edge, but the differences are less prominent.
2. Quality of Sound
Again, the Flip MinoHD is head and shoulders above the ZX1 in terms of sound quality captured. The ZX1 is still no slouch, and sound reproduction is perfectly adequate and useable for a camera of this size and for the intended market. But its microphone shows little regard for distant sources, and the person holding the camera can sound a little over-loud and distorted. The MinoHD doesn't have these problems, with distant and near sounds being captured smoothly.
3. Looks and usability
This is more of a case of personal taste. The MinoHD is smaller (about the size of a Nokia 6300, though a bit thicker) and probably slightly simpler, with a big red button for recording. It is also square on the bottom, which seems irrelevant, until you come to try and stand the ZX1 on a table top and you realise it will just fall over! The ZX1 has a slick brushed steel front, with sexy touch-sensitive buttons. It also comes in a range of great colours - I have the red, but actually think the yellow looks the best. However, the MinoHD's menus are more intuitive and quicker to navigate.
4. Features
The ZX1 features the ability to take still pictures, which is actually incredibly useful. Why the guys at Flip didn't think to do this is unknown, but it creates a massive weakness compared to their rival. Who wants to bother taking two cameras with them? Sometimes you'll see something that doesn't warrant a video, but would make a great still. Also the Kodak allows you to change the level of fidelity, meaning you can save on memory by recording on lower resolutions. Even better, it allows/requires the use of an SD card, which means you have virtually limitless memory. And it uses rechargeable batteries which are shipped with it, along with a charger! The Flip doesn't do any of this. The ZX1 wins this hands down.
The ZX1 is a great camera in its own right, but the MinoHD does edge it out in terms of performance and function, and would be the obvious choice if it wasn't for the lack of features. Its a tough choice, and really depends on what you intend to use the camera for. For long trips away from your PC, the ZX1 is the camera for you. If you are staying closer to home though, the Flip might be the better choice.