Things are hotting up on the lens market for the m4/3 system. Panasonic have brought out the 12-35 f2.8 zoom (35mm=24-70mm) and a nice lens it is too. I have to test this a little more but I would say that it is not made for landscaping. I think the very good 14-45 kit lens gets better results than the f2.8 zoom. Certainly I would use this lens when portraits are required and when the light gets a little low for hand-holding a slow zoom. I like the rendition and of course it's a f2.8 lens.
When taking landscape shots you will stop the lens down for optimal depth od field (normally) so this lens has no advantage against the 14-45 kit lens. It is heavier and the build quality seems better.