Chennai Express is a great movie... just as 3 Idiots was... both are commedy but completely different. The Starting of CE was slow but once Deepika enters its a complete laugh riot especially for those who are able to recognise the slight slangs and accents of different regions.

But authentically she doesnt speak in Tamil... she wavers between Tamil and Malayalam... I think... but still they took great effort to bring in the slight nuances of Indian languages...