True BEagle, and dont we dont just know. A340 and ancient DC10 are the only aircraft I've had to pass traffic info on a/c below controlled airspace as they couldn't even keep up with the climb profile on the SID.
Can't help but wonder how it would cope with an engine failure/loss of power. From an ATC perspective, better climb/descent performance makes it far easier to get yourself out of the proverbial hole!
(Not that performance is ever used to ensure separation of course..)