Yes, I've used it. It's available in most supermarkets among the spices, and if you can't find it there, Asian grocers will stock it. It looks like fine table salt, and can be added to any recipe as long as there's liquid for it to dissolve in. It's advised to use it sparingly - certainly you don't need to be as over-generous as some Chinese take-aways are.
problem with home cooking is when people say mmm thats nice its just missing something-they probably mean the MSG in the 'real' meal they microed last night.
I really thought people had learned about how bad MSG (in any form) is for you by now.
But it seems not.
MSG is especially linked to high blood pressure.
I would suggest using any other (natural) food enhancer,but NOT MSG!