This is a great tool, but has a few shortcomings that need to be addressed.
1) Keyboard shortcuts. This is crucial. We need a way to call up templates immediately, like command-shift-1, command-shift-2, etc. Ultimately, it would also be nice to be able to call up a template directly, like with a toolbar icon that opens and closes a side drawer with a list of templates.
2) The text quoting format for replies is a bit lame. It would be nice to use the standard mail quote formatting.

Overall, this is a good tool. It's just a bit painful to have to dig into a buried contextual menus every time you want to access a template. I hope this can be addressed for more efficient use. I just found out about this, and will probably buy it, but it would be nice to have an improved method of access.