Ok it will not replace a 12 string in a recording environment, but saying that, buried in a mix you really can't tell much difference between a 12 string electric and this .... as long as you don't go too high up the neck.
I also use this on acoustic guitar, where a little subtle use goes a long way. I put a TC spark in front to give it a bit more signal to play with and the results are really nice.
Be warned, this like the Digitech Luxe (one of my favourite pedals) are the 'older' current hungry pedals asking for 300mA, so if you have a 500mA power block it is a greedy little thing, which will starve your other pedals.
For playing live, it really can't be beaten, in terms of not having to lug around another guitar.
The main difference with this and an octaver is that the two top string are unison (+- a few cents for a chorusy feel), so you don't get that toy guitar sound on the high strings. Playing too high up the neck it does get a bit weird where very subtle is better.
All in all a very fun pedal and save a lot of hassle.
Highly recommended