are progressive springs or cartridge emulators worth anything on the katana front end? in fact, are the cartridge emulators any different than turning the valve at the top of the fork?
The emulators give you independent compression and rebound damping. They're "configurable" if you don't mind disassembling the forks each time. Unless you're a hard core track monkey, the single valve should work fine and keep the compression and rebound fairly balanced. You can also change the fork oil viscosity for another level of adjustment.
If you have any level of adjustability, I think emulators are overkill even for hard street riding. 0.9kg springs and 15w oil in my GS forks make me happy, even at Loudon, which gives the suspension quite a workout. Fully adjustable forks would soak up my mistakes better, but I prefer to reduce the amount of mistakes instead.
progressives.Dgyver and I installed a set in his Katana F/E and they feel great.