If you've been to one of my classes, you may have noticed that I never say namaste at the end...why not?
Mainly because I feel uncomfortable appropriating this term and presenting it out of context at the end of a yoga class. The cultural appropriation debate is a big topic of discussion in the western yoga community at the moment. I'm doing my best to be respectful in the way that I present yoga practices to my students and I feel that using namaste runs the risk of causing offence, intentional or not.
Secondly, namaste is usually used to say 'hello' - it therefore feels weird to say hello to a group of people who I've been in a room with for the last 60 - 90 minutes. According to Richard Rosen and Carlos Pomeda (and who am I to argue with these guys?) all the stuff about 'the light in me bows to the light in you' is somewhat overblown...colloquially it's just used to say 'hi'.
That said, it's true that the literal translation for namaste is 'I bow reverently to you'. For me it feels even weirder to say something to a group of students and expect them to reply in return that they bow reverently to me. No thanks.
Also, I believe that if we're going to use sanskrit terms in class then we should at least try to get them right. In 'Yoga FAQs' (you should get this book if you don't have it) Richard Rosen explains that it's not even grammatically correct to say 'namaste' to a group of students ('te' is the singular form of 'you'). Instead if we're addressing a group of people we should say namo vaha (I did try this once and everyone looked at me like I was mad...I won't be doing it again).
So this is why I steer away from namaste and why I prefer to sign off my classes with a simple 'thank you and go well'. It's easier for everyone to understand.