"Epic and frightening electrochemical hydroplane" is the best description ever - I know exactly how it feels, as if your feet are doing the cartoon "running in mid-air" thing.

Effexor is awesome for some people, and not awesome for others. (Same for any psych med, honestly. Don't believe the manufacturer's hype - there's a certain degree of suck it and see in psychopharmacology because we all have different brains.) Good luck with the changeover, and make sure the doctor or the pharmacist gives you clear instructions for the wash-out period, as well as the expected length of time for onset of the new meds.