SirDice has very nicely listed out the performance and management benefits of VLANs, but I would like to add the level of security management you can gain as well. Keeping workstations, servers, VoIP devices, and others (game consoles, etc.) in separate subnets can help minimize overall impact if something inside the network is compromised or infected. It's not a guarantee of protection, but if you have proper filtering between the segments of your network, you are likely to save a lot of headache, heartache, and productivity later when the next "Nimda" or "Slammer" comes along.

I say this because I think we will see an increase in attacks against platforms that are not running 'traditional' windows or *nix operating systems (IP connected game consoles, for example), and with the prevalence of these systems on your network, this could be a big deal. (My reasons for believing in this threat vector are diverse and I won't go into them here.)

So yes, let the vendors do the work for you. Don't sign anything yet.