Right (non-destructive) click sometimes registers no action, sometimes a rapid succession of right clicks, sometimes even a left-click (destructive!)

Confirmed so far on SMP, will carry out more testing to see if SSP affected.

Confirmed so far in Survival, will carry out more testing in Creative

Confirmed so far while holding torch in off-hand (as I almost always do), UPDATE: Also confirmed with nothing in left hand.

This is a challenge while trying to build, as 10%+ of the time when you right-click to place, even when the click is sniper-fast a second block gets placed directly in your face if you're at least a full space back. If not, block place gets rapidly followed up by a torchplace.

Trying to place a torch often rapidfires a second torch.

Trying to eat a peace of food more rarely leads to a second piece being silently eaten (since this is a slower process, server lag may play a role..)

Sometimes when you wish to place a block or a torch, you hold right for a fraction of a second only to notice no placement, but cracks just beginning to form on the block you were trying to place on, and a waving steve-arm, and arm slowly raising / weapon exhaust bar unwinding which indicates your entire half-second right click event was viewed as a left click.

This is a challenge when trying to either feed or shear sheep, as either it comes out only as a punch against the poor animal, or as a punch coupled with an instant shear/feed event. (via this I've learnt that frightened sheep refuse to mate until they've calmed down! ;P)