Or to put it another way - is there a benefit to alternating between e.g. the treadmill and the stationary bike, other than making it a bit more interesting.
I mostly asked because right now I'm splitting up a 1 hour work-out into 20 mins on 3 different machines (usually bike, treadmill, cross trainer). This is mainly to stop it getting too boring for me. However I'm not really sure if this is the most efficient since there's inevitably a few minutes of time whilst I'm swapping and I calm down/regain my breath a bit inbetween.