KingBuzzo, here's what I have seen so far. I've been following AT&T U-Verse for awhile since they use the Mediaroom software.
Can mediaroom integrate with media center?
Not at the present time. However I've read the the 2 groups will be working together so there's hope for the future.
What kind of connectivity/portability options for content is available with this system?
Mediaroom supports Whole Home PVR where you can watch a recorded show from any STB in the home. From other posts it sounds like MTS will not be offering this in the initial rollout in Portage, but will likely offer it later. If you are talking about making a digital copy to a PC that's not possible due to encryption. If that's important you could use the Hauppauge HD-PVR as discussed elsewhere on this forum.
Can you add storage?
No, but I've read that AT&T is now using 250GB and 320GB units, so MTS may also do so in the future.
Is is possible to display content/media from other sources in the home (pc...etc)?
According to the Mediaroom website "Microsoft Mediaroom connects your TV to your PC and other entertainment devices, giving you instant access to all your personal media so you can easily stream music, or share photos and videos with friends and family, on the best screen in the house." I don't know if or when MTS will implement that feature. It sounds like a nice feature for the techies among us, but I imagine the typical user would be a giant support headache.