Let me comment on the HL/Sixes issue:
I can see where valve is coming from. 6s in a way is like chess. It is perfectly balanced and the outcome depends pretty much 100% on the skills of the players involved (and their teamwork). It simply doesn't allow for many "new strats" based on items, unless they are perfectly balanced. Valve make their money from adding new stuff to the game. That is why Robin said that highlander is more interesting for him. I doubt he says this because he finds it boring personally. Highlander allows to give valve the data they need to finally realize that the Pomson is crap. This might actually lead to rebalancing with a competitive standpoint in mind and lead to new the new weapons and "strats" that were talked about, in HL as well as 6s. If people show interest in the "pub lobbies", maybe valve will even add 6s as well, especially if it becomes the new standard for lower level comp like lobbies are atm, which I can see happening.
In any way, it will raise awareness for competitive tf2 in general, and those who realize that they are actually good in valve HL can easily step it up to "real" HL and sixes, making the entire scene grow in one way or another.
Let's be realistic-basically no one on here who is into comp at a higher level already was really gonna play a "valve" 6s league (probably with no mumble comms) seriously, were you? It will simply boost the comp tf2 scene a lot if it goes well, and all options are open for the future.
/my3cents