I mainly use it with my Takamine jumbo acoustic electric for worship songs. I find it especially useful when I have another acoustic guitarist next to me. It gives your chords some different voicings and adds a little bit of "freshness" even to some old songs. 
 
Pros: 
- easy to use 
- high quallity product, feels sturdy and solid 
- "first aid" for situations when you don't have an arrangement for two guitars, and you don't want to sound boring with two guitars playing the same thing 
- encourages creativity 
- excellent for fingerstyle players 
 
Cons: 
- takes some time to get used to new chord shapes (if that can be a true con...)