That looks very cool. Is it going to crush my processor? I'll give it a shot after I'm done with my work.
Depending on size of your project and complexity of the code, we can update within <100ms to a few seconds after your keystroke.
No, all the processing is asynchronous.
That's not an answer to the question. If every keystroke kicks off a compile-execute-report cycle, then the processor (and drive) are definitely going to be taking on a lot of additional load. It doesn't matter that it's asynchronous; all that does is prevent latency between keystrokes so long as your machine can keep up with the additional load.
I use ReSharper, with pretty much default options because it's too much of a pain to figure out the magic combination of hundreds of options that will improve performance without disabling the features I like to use. ReSharper does its work on a background thread, but that doesn't stop it from making VS crawl when I open up a large solution after doing a scripted (external) rebuild. Async != Free Work.