I've had a few units get "stuck" on the border. They touch the border and then stay there, even though their target has gone away. Weird.

Also, you're right, Bhruic. "Works" is perhaps too strong a word, but its certainly so much better that you don't have to be an HA fanatic to use HA any more. A little tidying, a little wheeling, a little avoidance of borders and a little rounding up of stray units sure beats the intense micro of M:TW.