I think that in order to best advertise what you are displaying you need to make the distinction of what people will be watching.
For me, I think that you should have a multitude of "Top 10s" of all different types of plays, which then (after some arbitrary period) are compiled into a "Best of X period" montage.
This does a multitude of things:
1) Captures specific audiences and makes plays easier to categorize/find
2) Encourages people to come back for the "Best ofs"
3) Gives possible "contests" (Do X silly thing montage)
4) Allows for the most "top plays" to be displayed (I love seeing all the great plays!)
Categories are important, I loved how Machinima did the Halo 3 montages (Anoj). But I would have liked to see more compilations of the truly great plays (top ten of the month, top ten every 2 weeks).
MLG should be it's own category, not the only replays people are watching. Some of the best plays come from the general community, pro highlight plays are harder to find so you will have volume limitations, whereas, with the community, you may have too much volume (but you're guaranteed some crazy plays).
I would never make "Pro-only" montages.
