I used to be more OCD about it. When we have a bigger house, I want two trees... one being the super fancy decorative one and one being a memory tree. Right now we have mostly silver and red and then a bunch of random ornaments all around, which I actually like.
Anyway, I used to move all the ornaments around but this year I didn't. I let the kids do 75% of it and haven't moved any (except for a few clusters really low that Elijah has messed with). And it really doesn't bother me at all. I'd actually like to add a few other colors (turquoise and maybe green) and just have it full of ornaments... then you don't notice the clusters as much anyway.