I never comment on other blogs, because it seems too recursive for my defensive programming blood. That said, I was reading a fairly good criticism of FMC in the Telco 2.0 blog, but I think there's some FMC points that was missed, and in fairness, should be mentioned.
1) As I understand it, the largest customer complaint about current mobile service was that signal quality was low inside many houses. This is a big deal, since a very large percentage of cell phone use (something like 10-20%) occurs in the house. FMC directly solves this problem, and in my opinion, is worth the effort.
2) FMC means more than modal transparency - it means service transparency as well. I really would like to have my mobile phone appear exactly as my business desk phone. I would like both to ring at the same time, have the same voice mail, have the same features, work extension, DID, auto-attendant... everything. For me, this would be valuable.
That said, the Telco 2.0 blog is very cool - but I think just a bit out of bounds on this one.