When I wrote my book, I mostly looked at Cisco for this, and 
apart from Cisco to FreeBSD and Linux. The logic is that on a 
Cisco, you can build a good tunnel box (6to4 or manual 
tunnels) on a C7200 or some other box that has a decent CPU 
that can do the tunneling in software. Quite possibly a 
Juniper can do the same with hardware support (although I 
don't know that and it's also very possible that they can't 
do it in hardware or with decent speed in software) but there 
are no cheap(er) Juniper boxes that are suitable for 
deployment as a 5 - 200 Mbps tunnel box, in my opinion.
    

Are you saying that 6to4 relay servers should be dedicated to that task?
I.e. you should either dedicate a pair of routers per PoP or set up a
couple of BSD/Linux boxes per PoP?

--Michael Dillon