I used to have an 'M1'. Wonderful for the size, but one irritation which bugged me was the poor close-focussing ability: the M2/3/4 are better.
I actually sold it and invested in a second-hand Panasonic GM1 which is only a little bigger with the smallest m4/3 lenses, but gives much more flexibility (including close-focussing, of which I do quite a lot) and as a backup to my Olympus E-M1 body when travelling (they take the same lenses).
I can't speak for the USA, but there are a lot of GM1s for sale second hand in the UK now. The GM5 doesn't add much IMHO.