How much "acting" do you do as a GM?

Personally, I tend to simply explain what people say. I will occasionally put on a "gruff", "super bad scottish accent", or "dude with a deep voice trying to sound like a girl" voice for a few sentences, then I switch to "he/she says..."

I'd like to get better at this aspect, if only for immersion. Jon from 3d6dtl does a great job giving some of his characters great personalities through their voices.