I took Effexor XR for almost 2 years. It was great. There were some side affects for me. You have to understand, though, if a med says it "could cause mild whatever" I'll get it, and it won't be mild.
When I first went on it, and each time the dose was raised, I would feel sick to my stomach for some time during the day, this would last for a couple weeks. And the whole time I was on it, I battled severe constipation.
Other than these side affects, Effexor XR was wonderful. The panic attacks stopped, and my mood was lifted to the point, that I couldn't ever remember feeling so good. It was a miracle for me.