Traded my KTM690R for a KTM350 EXC-F...
Last year I purchased a leftover 2010 690R. After dropping an humping a few too many times in the CT woods, I realized I bought the wrong bike (that sucked!). The answer...the new 2012 350 EXCF. When I purchased the 350 in February, I tested rode both the 500 and the 350 at the dealer. The 500 was simply insane. The power was basically overwhelming and I found myself thinking how would I tame this thing on single track in the woods. The answer was the 350. Trust me...it has plenty of power. I geared the front sprocket down to a 14 and added the 2 position, thumb adjusted, mapping switch. For the riding I am doing here it is manageable and just excellent in the wood. Shedding the 60 lbs compared to the 690 has made a world of difference! Seriously, it feels like the RM125 I had as a kid... flickable and just much easier in the woods with all the juice I could want for hillclimbs, burms, whoops and all the woods riding I can handle.
I guess if your real power hungry and live out west where the riding is big... the 500 might be for you. It was just too snappy for me to handle in the woods.