See
http://www.icexpo.com/dvx100 for comparison pictures.
The Panasonic is full zoom through, $400, and only .8x wide-angle.
The Century .6x is part zoom through, $300, and super-wide.
The Century .7x is full zoom through, $650, and halfway in-between the other two as far as wideness.
The Century is a bit wider than the Panasonic, and 50% more expensive. In its favor it bayonets on/off very quickly, as opposed to the laborious threading procedure for the Panasonic.
The Century .6x is much wider than the Panasonic, and less expensive, and also bayonets on/off. But you only get about 60% to 65% zoom-through. After comparing them all, I came to the conclusion that the Century .6x is the best bang-for-the-buck, and if I want wide angle, I want WIDE, right? So why bother zooming through? But in retrospect, I think the Century .7x would be easier to live with, because you don't have to ever worry about your zoom-through. If the extra cost doesn't put you off, it's a good way to go. If you don't need that much wide-angle and you're going to leave the lens on a lot, the Panasonic is also a decent option.
