Yeah, I go to Gettysburg often, but I had not been there since August. As for changes, there are actually quite a few. The main things are exactly what you stated, the trees off by the round tops, and the fence lines. However, although I saw some new fences, there were also fences that were removed. When I was there in August there was a fence right next to the Hancock wounding site, and that was removed. But, the weirdest one that I was confused about, maybe someone here can help me on this, but there were so many cannons that were either completely removed, or just the cannon was taken off of the cariage. There were literly dozens of missing cannon. That was what struck me the most.
If you would like to see more of my photos from Gettysburg, please feel free to check out my site, http://www.virtualcivilwar.com Here is a direct link to the Gettysburg section if you like:
My first guess about the missing cannon barrels is that they were taken off to be cleaned, especially if the carriage is still there. They might also be preparing the carriage to get a touch of paint.