Like all technologies, it has its place, bandwidth reduction is a very viable requirement. I may just be a little short sided as I have mainly dealt with VoIP and have heard many carriers state that bandwidth is not one of their primary concerns.
Carriers are usually concerned about money, and how much they can make. w/o those value added features, its VoMPLS becomes less of a value proposition. Now if there was a method proposed to transcode the different packet types VoMPLS – VoIP, this could be very attractive.