Why dontcha start an oil thread whilst you're at it??!!!

Here's my take: bike gearboxes are designed to be used without a clutch. Upchanges are a lot easier than downchanges. Get an upshift wrong, it's not smooth. Get a downshift wrong and you can lock the back wheel up. Not good.
Try it:
Ride along in 4th at about 60mph.
Hook your foot under the shifter and apply a light upwards pressure.
Smoothly roll off the throttle-(it should snick into 5th)-roll back on the throttle.
Practise at different revs. You'll learn the best range to do it in.
The higher the gear, the easier it is.
Don't get lazy. Otherwise you'll get a sloppy change.
Downshifts? I wouldn't advise them.
(I know you weren't asking *how* to do them but, on the off-chance you didn't know, you do now!!)