I've read a few old posts about the issue of the front brake grabbing at slow speeds. It feels a bit like a warped disc but i don't think it is as you don't feel it at higher speeds and there is no pulseing thru the brake lever.
When i'm down to less than 10 miles an hour and virtually stopped it just feels like the front brake grabs a bit then releases a few times. I've scrubbed the discs and pads with brake cleaner just in case there is any contamination. Slight improvement but not much, may try changing the front pads, any ideas before i do that or take it back to the dealer