Upload & Sell: Off
I've never used the Panasonic 14-42, but for what it's worth I've read a bunch of opinions stating that it's more desirable than the 14-45. I can see that lacking IS on the 12-50 is a bummer (that's one of the benefits of Olympus bodies), but I don't think it would be much slower than a 14-42/45 and 45-XXX combo over most of the overlapping range. Granted, I haven't used a 12-50. If you get a G3 or GH2, you can get a 14-45 in the kit for next to nothing, so it doesn't hurt to start with that and see where you want to go next.
I believe you're confusing the 14-42 and 14-45. The 14-45 has better build quality, a switch for OIS and marginally better IQ. The 14-42 is the current kit lens. There appears to be a fair amount of sample variation, which confuses the issue.
The 12-50 is 3.5-6.3, which is somewhat slower than the 3.5-5.6 for the 14-42/45 and 4-5.6 for the 45-XXX
Existing OIympus bodies don't have a built-in viewfinder, which I find a major lack. I may wait for the E-M5, but don't need many of its features.
I'm not sure which camera system you're coming from, but in my opinion speed is pretty vital on m43. Generally speaking, the smaller sensors are not capable of achieving the high ISO noise performance you'll get on larger systems, and you're also diffraction limited around f/8-f/11. Fast lenses are the solution to both of those problems. The 20/1.7 and 45/1.8, at least, are must haves for their size, performance, and value.
I shot with Nikon film SLRs for many years, then sold all and shot with compacts for a while.
I want deep DOF for a lot of what I shoot (e.g., landscapes). The ideal lens for the interior of a Gothic cathedral for lots of DOF and no tripod continues to elude me. If I shot street, portraits, typical indoors, etc., then fast glass would be much more important. OTOH, the small primes seem to be very nice lenses.