Well, the rumors were correct, as we suspected.
Inevitably, the GF1 will be compared with the Olympus E-P1, but as the leaked specifications did tell us, the key differences are:
Panasonic GF1:

• Faster autofocus and tracking
• Higher resolution screen
• Built in flash
• Optional electronic viewfinder
• AVCHD video

• Supports autofocus on all Four Thirds lenses
• In-Body IS
• Stereo sound in video recording

But that is not all, Panasonic has published Micro Four Thirds lens roadmap for 2009-2010, among the lenses they are planning are:
• 7-14mm F4
• 45mm F2.8 OIS Macro
• 20mm F1.7
• 14-140mm F4-5.8 OIS HD
• 100-300mm F4-5.6 OIS
• 8mm F3.5 Fisheye
• 14mm F2.8
Along with Olympus 17mm F2.8 and rumoured Olympus wide zoom, I think the Micro Four Thirds is very promising.
Some previews from the web:
DC Resource
Lets Go Digital
DP Review