So the business model is that you are limited to how many numbers of projects that you can have going and strangely enough in number of drum kits...
There is a free subscription though where there is five projects available to work on.
It does not come with much in form of sound generators.
So far there is only one basic synthesizer and audio loops available!
Coming with a number of effects though.
But the strength of the application is the possibility to record audio tracks
and have direct collaborations.
So for bands that live far apart to compose or start collaborations with other people signed up it is great but like said not really with virtual instruments.
To mention to is that everything is stored in the cloud so you can jump from device to desktop etc.
Soundtrap are part of this video from Google I/O 2014 as can be seen here: