The main downside of this approach is that I wouldn't trust Voicestick -- or
any of the other "consumer" grade VoIP providers -- to not occasionally garble
and drop calls. Granted, the same thing can happen with regular cell calls,
although there it's due to getting in a bad area that the cell tower can't
hear well, whereas with VoIP you're at the mercy of what the Internet in
general is up to and may lose calls with no warning whatsoever.

So... fine for calling home or friends or whatever, not acceptable for
business users, in my opinion.