rrb555: we disagree, LOL
we've not had any happy clients with wireless IP phones or agent workstations or ISPs (ever). you may get away with it, but I really don't recommend it. Admittedly, we generally only get calls for negative experiences, so it's entirely possible it has worked for someone
IF you do it and it works, please do post your hardware (as many rooms have tried, and we've responded and found the problem with bad sound, or with time sync errors, or any other irregularities go away if the agent is hard-wired!).
Always have at least one hard-wired workstation for comparison in case of problems ... for testing. It could save you having to call someone like us!