First they asked you to share your experiences as a project manager. Basis this they ask you to come for a 2 day evaluation which they call as a workshop. This was a sheer waste of time. They kept discussing the Agile methodology very vaguely. Made a big show by writing down many worthless points on paper and sticking these as posters all over their meeting room walls. During this time the ThoughtWorks stalwarts manning the show were busy making mental notes of each participant. All through this farce people were kept guessing on who would get a call for the next level which is F2F interviews. Later all came to know that majority of the candidates selected were referred to ThoughtWorks by either existing employees or past employees.
The workfloor at ThoughtWorks is shoddy and is dark and gloomy. Also, at the end of the day they are a services company. Therefore their pay scales are not commensurate with the pompous and showy selection process.
If you are a senior applying for management positions then you should avoid going to their show. Only if you are working for very small companies, unsure of your future or have already been laid off you should give it a try since there is nothing to lose. However, leaving your cushy job for ThoughtWorks is the biggest blunder you could ever do.
This is a services company who undertakes projects from customers only if they agree to do them following the Agile (Extreme Programming to be specific) methodology. So they have a razor thin clientele. Not sure how safe it is for people who come on bench.