Rev-matching is fun as hell, but for an emergency maneuver the fewer actions the driver has to perform the better. I've 6th to 4th enough times to be able to do it at will, however I have never had to that under duress so even with practice I can't say for certain I would be able to handle a 6th to 3rd downshift when it really counted.
I know I wouldn't be able to. That's a lot to think about when you're mind goes into fight/flight mode. The other day I saw an STi (sounded heavily modded to) get cut off by someone in a very heavy intersection and he tried to maneuver and shift but stalled and got fender bendered. It was not a pretty sight.