Hiya,
I got my M1 visa back in February from the US Embassy in London. I found it all very straight forward - although there are quite a few online forms to be done before you go to the Embassy for the interview - which lasted all of 2 minutes! You need some passport photos for them aswell. The TSA took slightly longer, I got my training provider to do the fingerprints as they are authorised to do so. Can save alot of time when out in the states. For me the most bother was the TSA accepting a photocopy/email of my passport - took 3 or 4 attempts before it was accepted.
Generally I know that not everyone obtains the visa so quick - I think in certain cases it can takes months - and the Embassy are in no rush to give you answers or a timeline if this happens to you!
Good Luck!