I haven't worked with the IP DECT yet - just digital, but I've heard that it can be an involved process. Analog phones would definitely be simpler depending on their needs. If they expect to use them for call control rather that just making and taking calls, it will be more difficult on the end user.
If you're talking about the desktop IP phones, then yes - I've implemented many installations that use the switch port on the phone. Complexity will depend on VLANing, subnetting, and the caliber of the IT administrator. If it's a flat network, it's super easy. If voice is on it's own VLAN, the IT admin will have to create those routing rules. I've had a very mixed bag of experiences.
I don't think any of that was much help. I doubt I told you anything you don't already know.

I just didn't want to leave you hanging.
