It does not work at all for me on XBOX. I get no results at all, ever, even when sitting in a station where I just bought the commodity. I have also seen bug reports of it giving out false information.
I was also annoyed to see that it requires the player to have visited a given system before info can be obtained. If I have been there before then I already know what they sell! Sigh.
I guess we must still rely on EDDB for everything. Sad.