Not to speak ill about our new source of funds, but has anyone ever tried to by POS interfaces for PC? If you can find them, they are stupid expensive... Which leads me to the point, ethernet is no problem on PC's but any of the one-off's (ATM, T1/E1, etc) are quite expensive and hard to integrate properly (especially into God know's what stripped down Linux version/kernel they are running)
Also, look at the other risks, you primary routing environment is now running on "commodity" equipment. The Cisco hardware is hardened against environ and other things like that. I know that the hardware is going to work beyond what a hard drive, ram, cpu fan, etc will. Even if you do purchase higher end equipment, look at how often you are having to replace system components in IBM, HP, or Dell hardware? And look at your reboot counts. W/ swap files getting fragmented, buffers overflowing inside of unknown kernel paramaters/functions, and other misc "ghost in the machine" issues, is it really worth the risk?
This is the same reason why I use the best of breed approach to my R&S platforms. Cisco for routing (in my opinion, still better then Juniper) and Foundry for switching (because I can't afford the Force10 Hammer of Dawn
& they make incredible equipment).
Sorry, I will get off my soap box now.