When I open the app, I add a new preset to my list everytime, and I change my old presets. Adding and removing some pedals/amps from presets are really amazing. I think it is the most valuable app in the market. Wow!
This app is possibly the coolest thing i've ever seen, you can get the free version or the full version for about $30-$35. It basically has any effect pedal, stomp-box effects, simulators and attachments to any guitar you could possibly want. It also has a built in tuner, 8 track recorder, jaming station where you can play along to any song you have in your music library and metronomes and other stuff like that. It is definitely recommended. At least check it out or you won't know what you're missing out on.