Yes, beating HailStorm (or providing a reasonably widely-accepted alternative to it) is more important then being able to run .NET software. It's going to be hard to get right, but much, much harder to get accepted - and religious dogma will not help us sell the damn thing to service providers and users. Openness will help, but Jabber is not killing of AOL IM or MSNM. Price will help somewhat.
Can it be done? I think so. Note Apache versus IIS. Note DNS versus WINS, or TCP/IP versus NetBEUI.
Note also IE versus Mozilla. The desktop is our greatest weakness. We will need to work with IE to succeed. (We will also need to work with Mozilla to attract enough mindshare to get close.)