I don't know much about running steam servers, but will be able to allow more than 12 users in the server for chat purposes and such? Spectators would be fantastic, and it'd be super cool to be able to get some MNC parties going with the new client base that y'all will have.
Oxyteam's server will definitely feautre slight soundfile mods that proc Billy mays clips when you are hit by product grenades.
Dedicated servers allow for modded content to be downloaded to your computer whenever you enter the server. Many servers do small gameplay changes like custom soundtracks, different voice overs, etc. Some go as far to completely re-skin maps and change weather patterns. Some go further and mess with game balance changes rather than just ascetic changes.
But quite often it's a good/fun thing. You ever played on a Warcraft-based Counterstrike server? It's fun as hell.