well I'm on phenD but side effects are similar, my dry mouth isn't as bad as I've experienced with other drugs, lots of fiber helps alot.
I do have that heart racing feeling but my heart rate is not that elevated, its more of a pressure that wasn't there that actual racing.
I don't feel the energy either I'm actually more tired at night but once I go to bed I can't sleep. My Dr said that will go away when my body adjusts.
Overall I think it is worth it though, I don't think I could loose the weight otherwise.
Your doc wouldn't of suggested it if your heart wasn't strong enough. You'll do fine, good luck on reaching your goal!