mixing strains

So obviously people mix (breed) different strains together to get desired effects, but what about smoking two kinds of grass at once?
Has anyone experimented with smoking a heavy indica with a crazy sativa?
Do the effects add on to each other?
Mix?
Cancel out?
Multiply?
Theres some medical pot-ential.
Perhaps a heavy pain-killing indica could have its couch-lock effect counteracted with a bit of sativa in the vap?

errr umm.... wat?

Yeah dude I smoked two seperate strains, but when i mixed them, it was crazy. Kinda different but really great.