When it sounds natural it sounds VERY natural, and very "alive". Occasionally it crosses the virtual guitar "uncanny valley" and can sound a bit artificial, but that can be avoided by learning how best to use it. Assigning a controller to the strum speed is easy and allows for some very expressive tracks.
Dragging their feet moving this to 64-bit aren't they? I really want to use this moving forward as I have been able to make some really pretty stuff with it but I am shifting to logic and it is a "no go" under that host. I am sure many people are in the same boat. The workarounds are annoying, so I am a bit annoyed at them at the moment. If someone is in a similar situation that may want to hold off investing in Strum Acoustic GS-1 until they get it together and do a 64-bit version.