Sorry I wasn't in there longer... the baby's been having problems staying asleep. We're going through a "sleeping on the shoulder" phase for some reason. Plus we were packing for a trip to Durham this afternoon, so I was all over the place.
Agree on the shadows thing... and one of the best things about iRacing that I've noticed, is that they try very hard to optimize their graphics. In most of the updates, I've been able to improve my Frame Rates.
Also... I didn't think it made any difference until I actually tried it... but be sure, if possible, to hardware your computer to your router instead of wi-fi. REALLY cuts down on any blinking you may have and I think it has a small effect on frame-rates in official sessions too.
Oh yeah, turn off the "arms" in-car if you haven't already. That was a concession to the replay/youtube freaks that were boohooing because they didn't have driver animations for their videos.
iRacing, like real racing, is affected by your hardware. The better your machine, the more detail you can run, and the smoother your graphics will be. For example... VIR... when you reduce your graphics settings, you start losing track-side objects... like The Lodge, like the South Course paddock buildings, etc. So you start losing your visual cues that you might be used to in real life... and it makes a difference.