I made some very heavy, lined curtains for our old place and never got around to hemming them. I thought it was going to be an easy project. But I was wrong and I think next time I'll leave it to the professionals. I classify this project in the "just-getting-away-with-it" category (i.e. not going to not use them just going to cringe a little when I think of them).
I did eventually hem them, but not nearly as neat as the pros do it. This is one sewing job I'm happy to never have to do again, not because it's hard just because, well, I didn't enjoy it and wasn't completely happy with the way they turned out.
(I've always loved the light on the wooden boards in that house.)
So lesson learned? Get the professionals in for curtains.