I recently did some voice work for Ghostlady's upcoming game, Cliffhouse, and although I've acted in many plays over the years, I found it challenging to get the voices just right. I did read over the entire script several times, but without the benefit of working in a studio with the other actors there, it was difficult to know if my take on a line was the correct one. Also, considering all the different equipment used and the different acoustic environments in which the recordings are done, it's very difficult to get the same quality between different characters in a dialogue.
"Nanny Ogg looked under her bed in case there was a man there. Well, you never knew your luck."
-Terry Pratchett, Lords and Ladies