I'd advance that it's equally important, and maybe even more difficult, to play evenly and musically to very slow tempi. It's certainly true in drumming, and often neglected as a quality. Not just slow movements, but also holding off during long rests, only to come back in at the appropriate place. Not everything is metronomic, either, so accelerating the rhythm, or slowing it down, when the piece calls for it, are equally precious skills. Having decently-experienced colleagues helps, if all are to 'ritardando' in sync. If fast playing is needed, one may 'fudge' it with a half-tempo version. If slow is called for, it cannot be replaced by doubling up. The ability to play slowly is a great asset for any musician. Just sayin'.