I just played my first game of Network Test 1/Generator Defense. Unless something changes, it will also probably be my last.
It seems like it's running in "synchronous mode" -- just like online co-op campaign, and ODST Firefight, your inputs don't reflect in-game until they've gone to the host and back, resulting in input lag. i.e., you press the "jump" button, but it takes half a second before you actually jump.
This is exactly the reason I very rarely play Live co-op or Firefight. I can't deal with such latency between controller inputs and actual actions.
Synchronous mode might be adequate for cooperative play, as in the place it's been used before; but it is simply unacceptable for competitive game modes, as it puts everyone else at a *massive* disadvantage to whoever's hosting the match.
I'm assuming (and hoping) it's only in synchronous mode to facilitate the titular network testing; if Generator Defense shows up in the final game this Fall (and I hope it does, I love the concept of the gametype), I sincerely hope it will use "asyncronous mode" like all the other competitive gametypes.
[Edited on 05.14.2010 11:59 AM PDT]