It seems like a lot of people still don't know about this trick, so I thought I'd share it with everyone to alleviate some of the JIP complaints.
How to tell if you're about to join a game in progress:
When you're about to join a normal game in matchmaking (non-JIP), you will see several "Incoming Player" cards joining your party. You can't see their armor until map voting appears. Instead, you will only see player silhouettes.
If you're joining a game in progress, you will not see these "incoming Player" silhouette cards while you're searching. Players will instantaneously appear in your party with player cards showing full gamertags, armor, etc. Anytime you see this happen, without an "incoming player" card showing up first, you WILL enter a JIP game.
How to avoid the JIP game:
As soon as you've identified that you're about to enter a JIP game, immediately press start, go down to Network, and change your network to "My Xbox 360" instead of "Xbox Live". If you do this quickly, it will drop the search for you, at which point you can select "Xbox Live" again in your network.
This method doesn't actually sign you out of Xbox Live, so you don't need to reconnect each time. In addition, dropped games using this method do not show up as losses or incomplete games on waypoint.
I haven't played a JIP game since learning this trick (except for a few times where i just wasn't paying attention).
LOL at TC. Who cares man. I was glad to join a game in progresss yessterday cause it helped me get my 4/4 matches done quicker for whatever that was popping on my screen.
Also, JIP doesnt always mean one team is getting PWNED. I also JIP yesterday and the score was 50-40, not a big deal there.
If you want to join a JIP match, then by all means do it. The main thing that bothers me is joining matches that only have a minute or so left. I joined one with 5 seconds remaining once. It's just a waste of time.
Anyway, this topic is intended for the people who are complaining about JIP.