I guess it all depends upon the way in which it deals the "always on" part. Steam for example, assumes an always on connection as well, and is built around it. However if you want to take your PC away to somewhere without a net connection, or your internet goes down, you can put it to offline mode and carry on gaming.
As long as they have the backbone infrastructure (which supporting the existing xbox live service they probably do) to ensure it works, and allow something like this most will be fine. We already have to connect at some point to download dashboard updates to get our xbox online so that will be no different.
I highly suspect that the repercussions of being "always online" are being widely overstated in a bid to scaremonger. Those figures tell us who pays for the xbox live sub, not the number of people who have never ever plugged an internet cable into their machine, which i suspect most have.
Its not the fact it expects an internet connection that will be a problem, as nearly everybody does. The key will be how it deals with it, and what happens if you don't.