ive tried a number of software's, and nothing can do it really that well in real time, unless you are using a single instrument, only 1 note at a time, and close to a sine/triangle wave as posible.
melodyne works well for chords. But is not in real time.
There is also another bit of software for mac only caled Capo. which wont automatically convert it to midi for you, it will show you the notes played, and you can sorta draw on the frequencies, and it will output guitar tab.
