PSC runs DEC Alphas with gated. This is a supported but expensive option. Handy if you have a Cray and don't want a wimpy router in your FDDI path.
Expensive in terms of people, perhaps, in that it doesn't run out of the box. But once the config is made, it is fairly easy to maintain and has some nice properties that you can't easily find on vendor routers. They also tend to have bigger queues than vendor routers. On the downside, the newest generation of routers blows the doors off of the workstations, especially in terms of packets per second. (For example, the last years Alphas push something in the 3000-5000 pps range, where the vendor routers go 20-100 kpps. Don't know what this year's model does. Note that 3000 pps is full FDDI if people use reasonable -- 4kB -- packet sizes, though). The real rebuttal I wanted to make, though, is that the Alpha workstation costs in the $10K price range, with about $1200 per interface for FDDI (less if you can do the UTP business which alas we cannot). Compare this with todays prices on vendor routers and then tell me if you think it is expensive...
Avoid sys5 based stuff like Solaris and SGI Irix since it can't do CIDR routes and barfs badly on overlapped routes. Probably HP too. That leave DEC OSF and AIX. You could probably go with NetBSD on an older Sun. For PCs there is BSDI, FreeBSD, Linx.
I should add that we haven't extensively tested the CIDR stuff on our Alphas since we don't currently take full routing tables. But if Curtis says it should work I believe him :-) --Jamshid