I haven't gotten any real experience in either 6's or HL yet but I am an avid watcher of LAN's and general competitive TF2.
For the last few months I've been playing in Tf2Center and getting a feel for the more serious-scene and would really enjoy playing Scout on a more standardized level. I would also not mind playing Roamer but I know I need quite a bit of work on rollout's and things of that nature, but I find it fun and I have a decent enough game sense for it I think.
As for HL, I main Sniper in pubs or any Center's I can get into/host and am pretty good at the class, never really finding anyone that I have trouble sniping against as of yet in Center and definitely in pubs I would say.
Over-all I think I could contribute to a team and am willing to take criticism.
Well, there ya have it!