These two areas from CD Thayer's page
) are the most important. If the teeth are fine here I would say you are good to go. Both are visible with removal of the rear wheel without tearing into anything
This is what my pinion shaft spline looks like after I failed to lubricate it at the regular mileage interval.
Here's a look inside of the Propeller Shaft Joint, showing the clip ring that holds it in place on the Propeller Shaft. I ground a small set of clip ring pliers down on the bench grinder so they would fit inside of the joint.
After removing the clip ring, spacer and Propeller Shaft Joint, I inspected the splines on the drive shaft. They were not damaged, so my problems were confined to the pinion shaft.
The design is fine as long as it is maintained. Unfortunately your bike seems to fall into a period (2002, 2003 models) that seems to have not been initially molyed or improperly molyed by either the factory at initial assembly or checked by the dealer at the setup or 500 mile check-up. Some dealers don't even KNOW about splines and think you are talking final gear instead. A discussion over on the yahoo group earlier this year had several checking theirs and we found a few dry splines. In most cases they were caught in time. We even did a spline lube clinic at Kentucky Lake Gathering so many could see the process. Hey if this wrench wench can do it then you guys should be able to!
General rule is.. If you have the back tire off, check the splines while you are at it. Once the reccommended moly is applied you are usually good to go for many many miles.
CD's (aka Old Poop *G*) site has been an excellent source for the spline maintenance, along with a few others in the group.