I had the Panasonic GF1 first and purchased the GF2 after I broke the rear LCD screen on the GF1. Repair was going to cost just as much as a new camera, so I purchased the GF2 since I had a significant investment in Panasonic lenses. I actually preferred the operation of the GF1 (especially since the GF2 did away with any remote release capability).
Why would I have purchased the Nikon 1 instead? Primarily the built-in EVF on the V1, Expeed processor, and the dedicated speedlight. I almost always have a flash mounted on the camera, and though the Panasonic GF2 has a built in flash (better than the built-in flash on the GF1), I still attach an external Panasonic flash that is a bit cumbersome. The Nikon's flash is more compact and capable, and it's Nikon's iTTL system which I love.
The only thing that would give me concern about the Nikon is an expected lower signal to noise ratio and less dynamic range from the smaller sensor. However, the test results posted on DXO Mark show that the performance of the Nikon 1 processor is remarkably close to the larger GF2 sensor - enough so that it's a draw.