Mrs. Colleen's husband here... As long as this particular bike hasn't been thrashed (a lot of them have by now) it should make an excellent and reliable bike, especially for trackdays. Obviously, check for all the normal things you would look for with any used bike purchase. There's really only one thing to look out for:
Cam chain tensioner. They are notorious for failing. If the bike doesn't already have one, buy a manual adjuster from APE for like $65 and you won't have to worry about it. It's well worth the small price to pay to avoid a potential disaster.
I've had my bike for 7 years and have 32,000 miles on it now, and it's never given me any real problem, but here's a few more pointers:
The mounting tabs on the ram air tubes are easy to break from tightening the bolt too tight. I've broken a tab on each bike, but it will be fine without it.
A lot of people have problems with the neutral light. Mine works fine at first, but will stop coming on when it's hot. I've never actually tried to fix it though. Just know that it's common and is nothing to worry about.
The front tab that holds the airbox to the frame will probably not be lined up. On both my gixxers I had the bolt rip its way through the tab. This will also cause the air inlets to not sit flush with the passageways in the frame. It's fairly common and not an issue.
Definitely check the valve clearances. It's easy to check, but a PITA to adjust because you have to change the shims under the buckets, instead of turning an adjuster screw. But fortunately, it is common for them to stay in spec. I did my last check around 28k, they were all within spec and have never been adjusted.
A fairly common issue is trouble starting the bike when it's hot. One of the causes is the starter motor going bad. Even if you don't have problems, I would recommend removing the starter (it's really easy) opening it up, and just cleaning out all the dust that has come off the brushes. Get a multimeter and check all the plates for continuity too.
Another cause of difficult starting is improperly tuned carbs. One of the most difficult things to deal with is a used bike where you have no idea what the previous owner did to the carbs, but something is not right. If the bike's carbs have never been touched, you're in good shape. If the fuel mixture screws are exposed (some versions of the bike came with plugs over them) verify that they are set correctly. And definitely sync the throttle plates, they will probably be a bit out.
If you just have exhaust, a jet kit is not necessary. But you may decide to go that route for some more power. It definitely makes a difference. I have full exhaust and a K&N filter, so I added a jet kit, as recommended by Yosh. I have the Dynojet kit. I did all that 2 weeks after I got the bike and have been very happy with it, but I have heard that the Factory Pro kit is better.
You mentioned it has different headlight bulbs. If the wattage is much higher than the stock 50/55W, you run the risk of overheating one of the connectors. If you remove the lower left fairing, you'll find a large yellow connector. I can't remember which wire goes to the headlight, but that's where it would overheat. I just bypassed that connector for that one wire and used a larger single connector.
Of course you'll want a service manual. I have the Clymer and would highly recommend it. I've had a factory Honda manual, and for cars a Haynes, Chilton, and factory Chevy. The Clymer is the best one I've ever had.
The rectifier is a common failure. I've never had an issue with mine, but if you've got strange electrical/charging problems, start looking there.
Fuel pump gasket. This was a recalled item due to leaking and has probably already been replaced with the new 2-piece gasket. If you ever find some fuel leaking down the frame while the bike is sitting, that's probably the culprit.
