Or use Google Talk, for fuck's sake. The protocol is open, and the service is very reliable. I got all my friends running iOS to get Vtok, and now they can chat with me too. And you don't have to be on a Mac to use it from a computer - just log into Gmail or use any Jabber/XMPP client you want. I haven't used any other messaging service in over 5 years.
The only thing I use Google Voice for is the one or two friends still using dumbphones.