Yes, it IS the glass.
I shot my first show (Will Kimbrough and Brigitte DeMeyer) with my recently acquired 50-200 f2.8-3.5 (non-SWD). All I can say is the lens exceeds my expectations. Or maybe "BOOYAH" is more appropriate?
My doughty little 40-150 was producing solid, sometimes exemplary results, but I knew I needed the extra speed of the 50-200 as well as the better IQ it would provide, not to mention a bit longer reach. I knew from experience with the 14-54 vs the kit 14-42 that there would be noticeable improvements in microcontrast, color accuracy and overall resolution. The performance of the lens, both mechanically and optically, helps ratify my plan to use it with the EM1 as I continue to upgrade my gear.
I also put my like new E600 through its paces. I discovered some nice things and some niggles. I loved having 1/3 stop ISO increments, as opposed to 1 stop with the E520. Since I use auto-ISO when shooting performances, both the extra stop of ISO (3200 vs 1600 on the E520), less and less noise at the higher ISOs combined with the 1/3 stop increments to produce more consistent exposures as lighting changed or I changed field of view.
Here are a couple examples of the 50-200, cranked all the way out. Tests show that this lens loses a bit of resolution beyond 150mm, but I can't see it myself. The first is with the E520, then I switched to the E600 later in the show to see how the difference in ISO and grip would effect the performance of the lens. I know I'm not supposed to be able to use my E520 at ISO 1600, but Oh well.
I also like the cleaner E600 files at 1600 with a bit more DR than the E520. Now I am forced to give the older camera doggie treats to keep it from getting jealous.
E520 50-200mm@ 200mm, ISO 1600
E600 50-200 @ 147mm, ISO 1600