I always carry a Nikon D300S whenever I go traveling an most of the time it stays in the hotel safe as it's too big to carry around. Instead I carried a Canon S100 which whilst a great camera I found it was a little slow.
The GX-1 fits the bill, a great camera with some great results and with the power zoom you get 28-90 (35mm equiv) in a really small package.
I have since purchased a few more lenses and the electronic viewfinder (which is great as I need glasses for close work).
Also worth a look are Panasonic's additional wide angle and telephone "converters" which go onto the 14-45 power zoom.
Verdict: I love the GX-1 and whilst it doesn't have all the functionality of the D300S it is still a very capable camera and one I will carry around whilst out and about. I never thought I would say this but the D300S will be left at home now when I go on holiday. I have just ordered another GX-1 so I can have one camera with the 14-45 and the other body can be used with the wide angle or longer 14-175 lens. The best part is that they will both fit in a small bag and will be easy to carry around!