It came out today on the Genshi mailing list that Myghty performs far better than Django templates.
I personally think that the productivity improvements afforded by Genshi by things such as its match mechanism and the fact that you don't have to worry about XSS attacks fully compensate for any loss in performance.
However, I'd like to say something specifically about Myghty vs. Django templates. Both are good software. Both have friendly authors. I personally think in this case the performance issue is a red herring. If you can't trust your template authors to run with scissors, you should not use Myghty. If your template authors know the difference between a function and a dict, you shouldn't use Django templates.
I think that what the Django guys did makes a lot of sense for their situation, but using Django templates drives someone like me crazy. I like to create functions (containing re-useable bits of HTML) within my templates. I don't like repeating myself, even in HTML. Nor are custom tags a simple alternative. In stark contrast, Myghty's Component-Call-With-Content Arguments is frickin' awesome!
Ok, no religious wars. I really think you should just use the right tool for the right job!