It seems to be meant for research and development, not as the asteroid from the lex manpage. It would make sense as a teaching language for compilers, too. The people who need to know how Lex and Yacc work could read the Dragon Book later.

I wonder if Alan Kay and the Viewpoints mob knew about this, and if so, why they bothered with O-Meta?

It has been used successfully in production. According to this webpage http://www.infoq.com/articles/dsl-interaction-txl it was used for Y2K analysis and conversions of over 3.5 billion lines at IBM Global Services.

Edit: Better reference paper: http://ftp.qucis.queensu.ca/home/cordy/Papers/TXLSE_IST.pdf

Automagical is an Objective-C to C# source code transformation system that uses TXL under the hood.

http://razum.si/automagical/