Before you go to the trouble of acquiring a VM image of CUCM. CUCM by itself cannot peer to voip.ms or SIP trunk service. This is where CUCMExpress comes in to play. You will then have to trunk CUCM and CUCMExpress to get your SIP provider in. CUCMExpress requires a Cisco ISR router (26xx,28xx,38xx,39xx).
I've acquired a copy because I have a Cisco.com account thru my employment. But I have seen the VM image in sites that rhymes with " sit current". I honestly don't know why they just don't have this for free download since it's a demo.
A quick run down of features (at least what I use). You can run custom apps on the phones directly. I run weather map, live traffic info, live camera feeds from my BlueIris DVR and run Vera scenes from the phones. Of course the advanced calling features you typically expect in an enterprise phone system (call group, call park, music-on-hold, presence, remote calling thru VPN, voicemail, call routing, etc.
It is overkill for a home set up but this is home automation boards after all, everything we do is overkill.
You can PM me directly if you need more information. ^_^