Being Scottish myself, I find her accent atrocious. It sounds like a badly attempted Irish accent, actually.
It's funny you should say that because a couple of my American friends said exactly the same thing. I have to admit I found her accent pretty uncomfortable / forced, that's often the way though, the Alices, Mary Poppins & Berts Englih accents often have me frothing too. I guess it's the old thing where if you're a native to the character's land you always feel super-picky, but all the same it wouldn't be so hard for Disney to get this right and it *is* important. I hope they work on it and improve it with Merida though, otherwise it will look rather funny when she meets & greets with guests from Scotland. O_o