Lower back pumps suck when doing deadlifts and such. I stopped taking any "pump" product on deadlift day, it was so bad on time I had to lay on the gym floor for 10 minutes, I couldn't even walk.
A pro would be the fact that for me anyhow, a good pump helps with that mind muscle connection. I find I get more out of some movements when I am getting a good pump. Especially upper back and shoulder work.