The buell's are 984cc and 1203cc vtwins and as far as acceleration and on a track they barely keep up with most 600cc inline four cylinder engines. It's the nature of the beast, a vtwin has more torque, and inline 4 spins higher rpm and produces more hp. Typically, vtwin is good on the street and inlines dominate on the track.
HP = Torque * RPM / 5252
So either more torque or higher rpm will produce more hp. Inlines produce more hp than vtwins typically because they are able to rev thousands of rpm's higher than vtwins.
I agree with you, the performance is not lacking on the street, but if you ever get over 100mph just about any bike will smoke you. So going around a track where speeds are typically 75mph-125mph you will get beat most likely by 600cc, 750cc, etc bikes.