Midi Program Change. Every good sequencer, hardware or software has it, and is a must. It's mad difficult to change songs in a live set, then have to manually change patches on external synth. That's just silly.
Alot of sequencers send PC on song change (great!) - Some sequencers can sequence/automate PC (omg, even better!).
everything in above sticky list is a big YES and please implement..! but my goodness - Program Change has got to be in there!