We do prefix-filter all our peers, both customer and transit. We also
use as-path filters. It does seem to help us avoid insertion of invalid
routes and other issues (especially since some people we peer with don't
do the same on their side).
As far as stability and process problems, we're too busy working on the
instability of the Ciscos we're on now to notice, particularly the
problem with BGP scanner taking up all the CPU every 60 seconds. We're
preparing to move from an ATM core on Alcatel ATM switches with a Cisco
edge to an IP-MPLS core on Juniper M-20s with M-20s (and a few Ciscos in
smaller cities) on the edge. Hopefully that will improve our stability.
We're pretty excited about the Junipers (the network geeks like me here
Xspedius Communications Co.