I currently have an Olympus EPL1 with two Olympus lenses (9-8, 14-150) and a pana 20/1.7 lens.
If I buy a new Panasonic cam, a GH2 or GF2, can I still use te Olympus lenses, or would it be better to sell them as the Pan cams do not have IBIS?
Yes, you can, and they work just fine, but you'll need to hold them steadier or shoot them faster, particularly the one at 150mm. The Panasonic 20/1.7 doesn't have ILIS and it's still a great lens on a Panasonic.
Keep your shutter speeds as short as possible - possibly by raising the iso to minimise camera shake. We all managed without IS for years.
A 'rule of thumb' from film days was to keep shutter speed at least or faster than 1/f (f = focal length of lens). For MFT you double the listed f to get the film equivalent eg. the 14-150 should be at least 1/300 sec at the 150 end.
I have a similar question in my choice of camera body (don't have an mft camera yet). I like the handling of the GF1, but want the compactness of the Olympus lenses.
Answering the question, I wouldn't be too concerned about the 9-18 or 20mm: if you need a slow shutter speed, you would probably do better to use a tripod or gorillapod. I also find that for people shots, you need a faster shutter speed anyway to avoid motion blur (e.g. people blinking or moving their hands).
For the 14-150, I guess it would depend on what you're shooting. I've done a few tests lately on our Canon gear and found I can reliably hand-hold at 300mm effective focal length (i.e. fully zoomed in on the 14-150) using a 1/200 shutter speed. With ISO 800, that gives me reasonable if slightly under-exposed images in late afternoon light.
Perhaps you could try using your existing camera with IS disabled for a bit. I'd be very interested in the results.