Well, I think the part with bodybuilder isn't a problem since you could easily imagine Skynet creating a Terminator aimed at raw power - and that's just what Arnold's physique represents. I even think the acent is more of an advantage, in a way. It sounds a bit machine like, if you will, which just goes to reinforce the fact that this is, in fact, a machine.
Granted, a lot of that means that Arnold doesn't have much more to do other than cut out all emotions and let his presence work. Still, at the very least, the part was an excellent choice on his part.
I think one of Arnold's strongest performances is in Total Recall, actually. Don't get me wrong, he's no 'great' actor but in TR, I think he does a really, really good job of showing just how confused Quaid / Hauser is and how he tries to deal with the fact that his life seems like it's nothing more than a dream. I think the movie works in no small part thanks to Arnold's portrayal.