While we're on the subject of ball joints let me throw something out there for opinions...
I had read with interest the recent accounts of handling issues due to bad ball joints since I was experiencing what felt like the exact same thing on my 2007 GT (with about 30k miles), i.e. a very notiable slow-speed (30-50 mph) weave, especially obvious on smooth pavement. So bad in fact that at one point I even got off the bike and inspected the front end because it felt like something was coming apart! But at that time the front tire was extremely worn and was scalloped with very sharp 'corners' due to nomal wear, so I figured I really couldn't be sure of anything until I replaced the tire.
After replacing the tire the problem was dramatrically reduced, probably by about 95%, but some weave is still definitely present... but now I can't tell if it is abnormal or just a result of my looking for the problem. Maybe what I'm feeling was always there but just unnoticed, I can't be sure since I'm aware of the madness that comes when you look for a minor problem... meaning if you look hard enough you can almost always find it. The only bike I can directly compare it to right now is my 1100RT, but that bike is the most stable I've ever owned (almost to a fault) and the GT steers a lot faster, so maybe what I'm perceiving as a weave is simply a result of a quicker steering geometry?
What do you say, can you all notice any slight weave or instability at slow speeds on your bikes? I need to get this settled in my mind as I only have about a month of warranty left. I don't think there's much point in taking it to the dealer until I feel sure because at this point I have no doubt that I'd shoot an entire day and 200 miles of interstate riding only to hear 'feels OK to us...'