G1 telephoto lenses

I find the 45-200 kit lens much too soft above 150mm, and much softer than a Oly 70-300 I tried on a E-620. Since I mainly use it for telephoto (either for distant subjects or for macro, sometimes with a close-up lens), this is a big problem.

I can't imagine an Olympus 70-300 would work for me on the G1 since it doesn't have image stabilization, especially since for whatever reason I need much faster shutter speeds with the 45-200 (with IS) than I did with the 70-300 on the Olympus with in-body stabilization.

If telephoto and telemacro is important to me, do I need to look to a different platform for now (Olympus/Canon...) or is there another option? The butterflies and flowers are just coming out and I want to be ready.

Bob.