as a GXR user, i can share that the GXR + A12 28mm is very light and comfortable to carry everywhere but may be a little wide for some. the A12 50mm, perspective is just right but AF is not very fast. u have to be used to it.
The S10 is basically a PNS so IQ not very impressive if u're used to APS-C quality type pix.
for holiday, u're better off bringing the KX with 18-55 or a fast f2.8 zoom like the tammy 17-50 or da* 16-50.
the K-01 has its uses and the GXR is not really the same thing even though its smaller and lighter. the GXR k-mount, if it ever comes, is a very odd product to me... i don't think i like the idea of mounting k-mount lenses on a GXR. the balance would be awkward.