Other than price (which is significant), can anyone give me some advice or personal experience with these two lenses?
Panasonic HES045 LEICA DG MACRO-ELMARIT 45mm F2.8
Olympus ED 50mm f2.0 Macro 1:2
I've got a GF1.
I own both Olympus ZD Macros (35mm f/3.5 and 50mm f/2) and have used the Macro-Elmarit 45mm quite a lot too (loaner from a friend) with the G1 body. I use the two SLR lenses with my SLR bodies as well as the G1.
The Olympus 50/2 Macro is superb. One of the finest 50mm lenses I've owned (which includes a lot of excellent lenses over the past four decades...). However, on the GF1, it is manual focus only, will reach 1:2 magnification (and neither the EX25 or EC14 are usable with it on the GF1), and it is somewhat bulky and heavy with the GF1 body. No matter what its price, you have to add another $130-160 for the adapter too.
If I were buying a lens specifically to use with the GF1, I'd pick the ME-45 without question. Superb rendering, very sharp, autofocus capable, 1:1 capability in the lens, image stabilization and focus limiter for general purpose shooting, small and light. I'll add one to my kit sometime soon.
(BTW, I've also used several manual-focus, adapted macro lenses with the G1. Both the ZD 50/2 and ME 45/2.8 out-perform them without question. And they were not poor performers by any means!)