I'm in two minds about this as well...

For me, I find it helpful to make noise and I have quite short labours, so it's not like making noise will take away from my pushing ability or slow things down much. Last time I had a midwife tell me I would hurt my throat from the grunting/groaning. As if I would really care about the pain in my throat as opposed to the other end!

Now I don't know what to do this time, as that midwife has made me feel quite self conscious...