I posed the question to my dealer about the pulling to the left or right on the GT/GTL and here's the response from a very good technician that I trust:
...this is because the rear drive is off center just like every other BMW built. The shaft has to be off set to compensate for the front to rear wheel off set. So they all have a tendency to pull to the right or left depending on which side the drive shaft is on but you don't notice it over 40 miles an hour. It also depends on the air pressure. The Master BMW Certified Technician has spoken.
However, I've never noticed any pull on my LT nor heard of it as an issue with other LT's (or other beemers for that matter). Dunno. I'd hate to pick mine up and find it to be an issue that I have to deal with for the life of the bike (or me for that matter).