Aside from the differences in lens size, these bad boys are all pretty much the same, hitting the ground with 12 megapixel CCDs, 2.7-inch displays, advanced face tracking, intelligentautomode, and both xD-Picture Card and microSD compatibility.
While we're at it, we might as well mention the company's newest addition to the mju line: The mju 7010 sports a 7x optical zoom, but otherwise looks pretty much the same (12 megapixel, 2.7-inch display, advanced face tracking and intelligentautomode, magic filters, etc).