12 MP Lumix GF1 adopts the Micro Four Thirds System standard
My experience with DSLR cameras isn't extensive since I'm a point-and-shoot kind of girl but I think it helped me look at the Panasonic Lumix GF1 from a more casual perspective.
Here's a techy introduction from Panasonic for its Micro Four Thirds camera:
The GF1 adopts the Micro Four Thirds System standard, which was developed as an extended version of the Four Thirds System standard for digital camera systems. By using this standard and developing a camera body that eliminates the mirror box and optical viewfinder unit, LUMIX was able to achieve a dramatic reduction in both size and weight compared with conventional digital SLR cameras, to create a new-generation system camera that features Full-time Live View, high-speed, high-precision Contrast AF, HD movie recording, and more.
To put that in plain speak, it boldly goes where other professional cameras haven't gone in a long long time - a ladies handbag. And this 12MP digital camera comes with a handy intelligent auto mode so you don't have to don your professional photographer hat to get it to do awesome things.
The fixed focal lens (20mm) means you can't really zoom and get really into the close shot you want, and it can get a bit shaky if you're not sure of what you're doing (ahem). Features like face recognition, the intelligent auto mode and AF Tracking (that lets you keep a subject in focus even if it's moving until you press the shutter) means that the GF1 also appeals to a more mainstream audience.
I've yet to find a professional photographer that would make it their weapon of choice. It's somewhere in the middle of being a regular point-and-shoot camera and a DSLR, but can't fully match either. It really doesn't need to though because it's another alternative and having options is good from any perspective.