My experience with iOS 6 Maps:
Bay Area - pretty good
National Capital Region - okay to good
Baltimore - marginal to okay
Frederick, MD to Harrisburg, PA - sketchy to marginal (did some things very well, but it also got me lost a couple of times and sent me down roads that didn't exist anymore. When it sent me down the non-existant road, it just stopped working altogether. I guess it wasn't embarrassed.
Turn-by-turn spoken directions - devours the battery (or rather the...