OpenBGPD itself was solid and looked at lot easier to configure than the alternatives. Can't remember whether I looked at Zebra or Quagga or both though.
Haven't used OpenBSD itself since those days either, but OpenBSD originated software tends to have that straightforwardness I miss sometimes.
What about non-free?
No problems what soever in the almost two years, they have been running...
Notice we are a low traffic site and are only running 1Gbps on all links currently... (but that should not matter as load is almost unmeassurable)
* = a "default route"
I pay around 250 USD per link per month each, but you also need AS-numbers and IP-addresses, in RIPE (I am in Europe) that is ~2k USD more per year..
We run it on the global network I manage, mostly not in the core (hardware routers are required/better at our scale) but we do run BGP on edge devices and use BIRD there, in a number of full-FIB situations as well.
I will also say i've run OpenBGPD in the past, albeit in less demanding situations, and it worked well. That said, I don't recall any advantages OpenBGPD offers over something like BIRD and it was considerably less flexible, though that may not be so anymore.
My Quagga setup was fantastic! I used linux-ha to do fail over routing, and could do kernel updates and reboots with, as far as I could tell, zero lost packets. I was super happy with those routers!
Do you mean Juniper's JunOS (FreeBSD based), Arista's EOS (Fedora based), or Cisco's NX-OS, IOS-XE, and IOS-XR (Wind River Linux based)? Those are all non-free BGP stacks from what I know.
Or perhaps you meant something you can load onto a regular old Linux/BSD distribution.
It is reliable, secure, well-tested, and BSD licensed.