We did the same thing just be careful to remove any entries in DNS relating to your old server (tftp was effected for us) - we missed one entry and the phones kept pulling in the old tftp address, causing slow phone boots and failed services - other than that, it went well. I would suggested making the changes to dns, flushing the cache and makeing sure they take effect. It will give you odd issues otherwise.
Good luck!
Gerri
