I'm running a Pro600 in my 3330 this year. We've had minor issues with the guidance. At one point I simply lost GPS heading. After several attempts to install old software, new software, new NavII controllers, and even contemplating a new Pro600, they simply put a new 262 receiver on the roof and voila!, it worked.
You most certainly can be creating a boundary and A-B, or Swath, or Curve lines at the same time. I do it in multiple fields every day. The only major disappointment for me, having run an AgLeader Insight last year, was the lack of Application Reports. I do lots of custom spraying on the side, and I don't have any way to enter weather conditions, soil conditions, notes, etc like I used to have on my Insight. Otherwise, I'm impressed with the Pro600.