A lot of people find that this is fun, though it does alter the experience. It can make the experience a little less "messy" if you've had a really strong pill, but it can also make the pill feel less loved up. Too much speed overwhelms the pill to a significant extent --- you can still feel it, but it doesn't appear to be the predominant effect. Small amounts are good though, especially on the comedown.
Just be aware that it does place extra stress on your cardiovascular system, and that the effect the speed has on your body raises your body temperature.... high body temperatures can exaccerbate neurotoxicity (if it occurs). Given that high body temperature appears to be a precondition for MDMA neurotoxicity, I'd suggest that doing pills then having heaps of speed and jumping around all night -- and getting really hot and sweaty -- isn't the best way to look after your brain.