The voice for John is really good. He sounds sort of like what I think Martin Freeman would sound like if he were French, which is highly appropriate. He has a good grasp on the frustration, the charm and the sarcasm. Sherlock's voice is okay, the right timbre, but I didn't get a chance to hear him rant or be bitchy, so I'm reserving my judgement. There was no Mycroft or Lestrade to judge and Mrs. Hudson only had one line, but Sarah seemed very good.
I often wonder if people who haven't heard the original actors speak find that the dubbed voices don't match or not. Like, on SGA, the actor who dubbed Ford had a very deep voice, deeper than the actors who dubbed Sheppard and Ronan. It seemed really out of place to me, but for someone who hadn't ever heard Rainbow Sun Francks speak, was it out of place for them?
In terms of translation, it seemed to all make sense. Sherlock's little stream of consciousness floating words popped up in French and so did Moriarty's text message at the end. I always like to hear how they handle very English names. Everyone was good with 'John', and there was a general consensus that 'Sherlock' should be pronounced with an emphasis on the 'ock', but 'Holmes' was all over the map, from 'oms' to 'ohms' to 'ollllms'. And 'Sherlock Holmes' tended to come out 'SherlOCKoms', which sounds like a cute little nickname his mother might have given him as a baby. Which Mycroft would then pull out every once in awhile to annoy him.
While I'm on the subject of Sherlock, I've been trying to figure out where John works exactly. Is Sarah a GP? She seemed to do the hiring, so is it her practice? Or does she just work there? Are there any other doctors there besides her or John? Non-sequitor: I'd forgotten she goes after the Chinese smuggler with a stick. Why do people not find her awesome?