Ascend GRF

I've been hearing conflicting stories about the Ascend GRF lately. Cisco claims that it doesn't really work as advertised in "realistic networks," but Ascend says this is because Cisco's routers melt down when the GRF feeds them routing table updates, so the GRF has to be throttled back to work in a mixed environment. Does anybody have any real experience here? Any information, pointers, anecdotes, or wild rumors would help. Thanks, -Peter