I don't like voice overs.
To me they're a cheap way to tell a story. They're a cheap way to let you know how the character is feeling.
I'm not saying voice overs can't work... I'm just saying I think most of the time (97.54% of the time) they just don't cut it.
There are different ways to allow the audience to know what the character is feeling. Different cuts, different looks on their face, different reactions... Lets give the audience just a little bit of credit here.
Don't let the character flat out tell me he's sad, pissed off, or lonely... Let me see him feel this!
Show me, don't tell me.
I'm not going to lie to you; I've put voice overs in scripts. It never went beyond the first draft though. Imagine your movie with the voice overs, it's almost as bad as breaking the fourth wall and talking to the audience.
It may seem really cool and you feel like a genius writer, but in most cases it won't work and it's cliche'.
Will this scene be more powerful with the character telling you everything from his soul?
Probably not, no.
Would Luke Skywalker's approach to Uncle Owen and Aunt Beru's dead charbroiled bodies be more impacted to you with his voice over telling you: "I can't believe this. They're dead. My vast amount of loneliness drives through my body like a pod racer at the Boonta Eve. As now, my last remaining family, is gone. I need to go with Obi-Wan to become a Jedi Knight."
Yeah, see, that wouldn't really work.
Be careful with voice overs. They can kill a good script.