[hardlydangerous]

I use the clutch from first to second, and then never again on the way up. One of the prime selling points of sequential transmissions (like in motorcycles, or really fancy aftermarket car transmissions) is the ability to upshift sans clutch.

Your car's transmission is NOT a sequential transmission, and really shouldn't ever be shifted without the clutch. Is it possible? Sure.... but it's not wise, even in racing. All formula cars, as far as I know, use sequential transmissions anyway. I know the top level stuff does, and I know that Formula Ford cars do, but I don't know about others.

A cars transmission is a constant mesh transmission just like a motorcycles.
the difference is the syncros that match the speeds of the gears to reduce notchy shifting. Again no syncro gearboxes are used in racecars.
Syncro gearboxes are not used in bikes because of the huge weight difference and size. Sybcros are used to make the transmission MUCH more reliable just as useing a clutch with a sequential transmission will.
sequential transmissions still require a pause in load/torque to shift properly. if you letting off anyway why not blip the clutch while your at it.