Shift kits.. do you really need one????

There's a lot of talk about the TF-2 shift kit, nothing wrong with it, if that's the type of shift you want. I've got the little kit in my 74 Challenger, the SK-TF. It was put in by a talented transmission builder, and it does exactly what it was intended for, reducing the overlap time between shifts. Under normal throttle, the shift is quicker, but not harsh, however, under full throttle it'll bark the tires.
The TF-2 was intended for heavy duty useage, such as in trailer towing, 4x4 situations, and those that wanted that kind of shift in their car. Originally Transgo had 4 shift kits for the TF. There was the SK-TF, also known as the builders kit, the TF-1, the TF-2, and of course the TF-3 for those that wanted a full manual valve body.
IMHO, if you're not beating on the car, but want to improve the shift quality in your TF, just install the SK-TF kit. It'll cut down on the overlap, but won't give you a hard shift unless you're under WOT.
Installing or not installing a shift kit is usually the builders option, based on the information received from the car owner, and what the vehicle is being used for. In the almost 30 years I worked in the industry, there were builders that installed kit in every transmission the built, and others who didn't unless the customer wanted one. In this era though, it seems like every transmission has issues, and shift kits are available for all transmissions to help cure these problems.
As it was mentioned before, factory transmissions usually had a nice soft shift. God forbid you should feel the transmission change gears, and while this may have made the owner feel good, those long overlaps and soft shifts weren't doing the friction plates in the transmission any good. By the way, a shift kit won't really help a transmission whose life cycle is just about finished. They don't make a bad transmission good, but will make a good transmission better.