Granted, there are restrictions. However, a lot of those restrictions have disappeared in recent releases, and more are disappearing all the time. Iterators, generators, xrange, I expect those all to be included in due time. Additionally, re: the standard library, there is a project called Ouroboros[1] that replicates the standard library in pure python, and there was discussion regarding integrating that into Transcrypt.

You're right, it's not there yet, and I'm interested in it for purely theoretical reasons (I personally don't think I'd ever use Transcrypt for anything in production), but I think it holds great potential.

[1]: https://github.com/pybee/ouroboros/tree/master/ouroboros