RTMFP is very exciting for P2P multiplayer games but at this point I don't see a lot of choices for actually using it.
The Stratus service is basically meant for experimentation only, while hosting companies that offer FMS support are usually geared toward video/audio streaming, with plans&prices structured accordingly.
As a developer of a small game, I'd love to add P2P support but only if I can find something free or inexpensive.
In theory, Stratus/RTMFP is ideal for small games & budgets - interaction with the server so bandwidth/CPU/storage is very low.
In practice, even something very cheap like Influxis.com has 256 kbps streaming for $6/month, but they only offer FMS 3.5...
Edit: digging around, I found LiveCycle Data Services. Is anyone using it for a real live game? What are the typical costs?