I would add that in some ways that the way it can store four different selectable settings is very similar to the Boss Katana with it's four buttons and the way the amp models are selected is also very much the same too. I have the Katana 100 head with the little 5"speaker which is more powerful and a bit bigger, but without the practice and jamming features on the Spark.
I have opted to programme four different sounding amps, a Vox Shadows type with the echoes set to roughly Echomatic 2, a Fender Twin with tremolo & reverb, a Marshall Gary Moore sound and a clean acoustic rhythm with the option of adding a bit of chorus. That way I can use it for most practice sessions and recording on my computer. By adding my TVS3 and just using the Vox AC 30, without the Spark's effects, I have all the control over The Shadows sounds I would ever need.
Last night I wanted an instant Chris Rea sound to record the guitar part on 'Let's Dance' and just looked at the available sounds in the library on the App and found one instantly. You can do that with almost any song if you're looking for the right tone, you just search the App and a list appears from which you can choose, then if desired edit to your preference.
I keep saying it, but it's a great time to be a guitarist with all this kit available to help us.
