I drove my first RX-7 for 6 months with no clutch. Got so good I could upshift, down shift, anything I needed to do. Got the money together, put a clutch in it and never had a single problem out of the tranny.

It only destroys your syncros if you can't find the gears and short grind going into gear everytime. If you learn your RPM points, you won't destroy a thing. If i'm lazy, I do it in my boosted 4Runner sometimes. The look on folks face when my foot is on the dash and i'm going through gears is priceless.