I've been up George Creek to Trojan Peak. The bushwacking isn't that bad, if you take the time to try to stay on the use trail where there isn't snow coverage. You have to look carefully for the right places to cross the creek to stay on the use trail. The five creek crossings were hard for me because I hate log crossings. Overall, it is a pretty tough haul, but not because of the bushwacking - it's the combination of the creek crossings, rough trail, a bit of bushwacking, heavy pack (if you're backpacking), hot temperatures, and side-hilling in the snow where there is snow coverage that makes the first part of the journey difficult.
We camped at about 9500' and were tired when we got there. From 9500' to Trojan, the route is wide open and travel is relatively easy. I really enjoyed the second day of our trip up George Creek. The route over to Williamson doesn't look to be much more difficult than the route up to Trojan and Barnard.
Anyway, it's beautiful up there. I was going to head back up this year, but the high winds got in the way last week; so now it'll have to wait until another year.
Here's some pictures from our trip a couple years ago:
http://kathywing.smugmug.com/California-Hiking-Scrambling/Sierra-Nevada-Hiking/Trojan-Peak-13947-via-George/4925637_HuWam#294296460_cyXge
It was 7 miles with 8000' elevation gain from the trailhead to the summit of Trojan Peak (one-way). You'd have to add about 400 or 500' elevation gain for Williamson, but the mileage would be similar.
I would be tempted to try it as a day trip, except that would require me to cross the creek those 5 times in the dark either on the way up or on the way down and I'm not willing to do that. If you're fast, you might be able to do the entire trip in a day without spending time in the dark.