My first foray into IP systems was a VentureIP box. IFM. You plug in the controller, plug in the phones, add the power and voila! Building the infrastructure was still an issue, powering the sets is retarded, especially if you use the "economy" PoE switches (read HP FS108), but all-in-all, IP systems require very little in terms of setup internally.
QoS and trunking may be a different issue.
LkEErie