You may want to consult this Popular Photography review on the 31/1.8 Limited lens:
Looks like a stellar performer, but I find the price unpalatable. Still, Pentax has a digital upgrade path, Contax G doesn't, all the rumours flying around notwithstanding. I have both and I only wish there is a digital Contax G but as it now is I probably won't "switch" but keep both.
My gripes with my G2: no finder display of aperture, no flash exposure compensation for fill flash, no display of how many stops over and under in finder (actually #3 if present can alleviate #2, but unfortunately G2 lacks both), and you must learn how to use a center-weighted meter (no matrix automation no spotmetering). Other than these deficiencies G2 handles much better than my PZ-1p body. I like the rangefinder idea far better than SLR.
Optically I have yet to see any Pentax surpass any of my Zeiss lenses (21/28/45/90), but then I have no experience with the Limited series because they are too expensive. I do have a few top Pentax lenses in their * series, though. The Zeiss lenses are very reasonably prices for the kind of optical quality they offer. Even if the Limited lenses can surpass Zeiss they won't do as well with the performance/price ratio.