In terms of FOSS routing platforms, I think Vyatta has a better user interface than Mikrotik. IMHO if the CLI is awkward then there a higher risk of misconfiguration. I haven't used either enough to comment about stability.
Jonathon. This email and attachments: are confidential; may be protected by privilege and copyright; if received in error may not be used, copied, or kept; are not guaranteed to be virus-free; may not express the views of Kordia(R); do not designate an information system; and do not give rise to any liability for Kordia(R).