The larger competitive issue with lobbies and pugs is that people do not receive skill-dividing accolades for playing well. While providing servers allows for players to quickly jump into the competitive scene, it's not the definitive cause of why these types of services stagnate. As such, your primary focus should be on the matchmaking service.
Will matchmaking divide players in different skill brackets?
Most importantly, will your ranking influence matchmaking in a significant way? When people adhere to the 6's and HL formats, will their matchmaking be influenced separately from "pubby" servers?
Implementing the Elo rating system into your matchmaking system will not just usurp TF2Center, and possibly even the IRC pugs, but also provide a long-term, scalable service to the competitive community (i.e. you'll constantly receive a fluctuating, unique stream of visitors to your site until it's implemented officially.)