so im torn between the panny and the new olympus 300mm's. from what i gather, focusing is slightly faster on the oly, and its POSSIBLY sharper, and most of all, lighter. BUT the faster panny keeps taunting me.... my finger is hovering over the buy it now button for both of these, i want to order one tonight! or...asap. haha primarily ill be trying to shoot birds. other wildlife. but if i got the panny, would i be able to shoot high iso, at the low end of the zoom, in lower light? i know f4 is still pretty slow in that regard....but it would be cool to use this at a concert if possible, even if i do get grainy images... help me choose?