LS suspension is probably a little better for the track, but honestly you won't miss it if the regular is all you have driven. If you get a regular one, make sure it has the Recaro/Torsen package since you will be tracking it and add the brake ducts and tranny scoop. You will also want a more open grill if it is a 12, otherwise you have to pull it out at the track on hot days.
Common issues? Passenger side head ticking is bad, some of the trannies are a little notchy and some will get lock outs at high rpm when it is hot, but not sure if they correlate. Make sure it was serviced, depending on miles. The Recaros sometimes wear where the belt slides over the shoulder. MGW shifter is a good mod, from what people have said here, though I don't have it yet. Some rear ends whine, that is bad. Can't really check it easily, but some burn oil. Mine burned 5+ quarts in 2500 miles, then not a drop since doing the first oil change. Rattle from the passenger side at 2500-3500 rpm is the bolt on the passenger side side pipe, it is easy to fix by twisting it a little. I had a leaking caliper but it is the only one I have heard of, I'm almost certain the bleeder was cross threaded from the factory. Black specs in the paint, I was able to get almost all of them out with a clay bar but not everyone has been as successful. Try to drive it a few miles on the highway at 4k rpm and see if it throws codes for crank sensor, that seems fairly common. Some have the rear end not quite centered right, not sure how common that is but it has been mentioned. I don't remember what other common issues they have.
It is a great car, I cross shopped a LOT including more expensive cars and there is nothing that combines the looks, attitude, and just plain fun of the Boss without spending 3 times the money in my opinion. But it is more of a sporty GT than a true sports car, due to the weight and size. The weight is the biggest minus on the car, both for twisty back roads and for the track (mostly due to stress/heat as a result) but it is still a lot of fun for both, and the easiest car I have driven on the track that was not AWD.
I would have gotten an LS if it were available in the other colors, and didn't have 20k markup at the time. But just because I think it is cool, I am happy with my regular Boss.