Should I stay or should I go now?

My carry round camera. A Panasonic GF1. It's been a trusty companion alongside my Canon gear and great for those moments when a full dslr kit is just too much to hawk around.

I really enjoy using it.

Question is, as I've got an opportunity to spend some cash, do I upgrade it to the GX1 with the improved sensor? I have a full compliment of Panasonic and Leica lenses for the m4/3 format so going to stick with this type. I could go Olympus too or just stay with the GF1.

Decisions, decisions...

Any help or advice gladly received : )