There are definite problems with the service. Problems that don't surface once you dug in and started using it for a while with people knowing only your GV number.

    1) Inbound texts occasionally arrive late or not at all.
    2) Google Voice Android App sometimes breaks silently so you can't receive 
    calls or texts until you relaunch the app.
    3) Sometimes you can't make outgoing calls through the GV android app.
    4) MMS messages sent to you are rejected. Neither you nor the 
    sending party are notified that anything went awry.
    5) No confirmation that your text has been sent. 
    Sometimes GV lets you know that it failed, sometimes it doesn't show up in your 
    conversation but has actually gone out.

    Additionally there are missing features:
    1) A bunch of non-google services don't recognize GV numbers as valid and 
    will not accept it as a phone number.
    2) MMS sending and receiving.
    3) International texting.
    4) Android App with clear semantics what constitutes a conversation and a 
    clear history of what you sent and received.

I should add that these issues have existed for a long while and there has been no communication from Google about resolutions to them. Not sure if there is any development going on the backend, but the android app development hasn't moved in the past year.

Other than that, it is a great service at the price of 0 dollars and non-trivial frustration.