I'm sure a lot of people will agree with me in saying that the new method added onto finding a game is awful. Joining games that have already started does speed up searching times. However, is that ever a problem with a game that's just been released and especially a game with a pretty sizeable community.
The only time a game will have free spaces is because somebody has A) quit by choice or B. lagged out/disconnected. Therefore, the opposing team is bound to be either winning to make a player quit or have capitalized on a player lagging out. So the odds are joining a game that has already started you will be on a losing team were further players will either quit or you join the game that late that regardless of your efforts the opposing team would have already won.
Losing is never fun although some players won't mind losing to others it is frustrating. Overall, the game is great and plays out fine however I would like 343 to either get rid of this possibility or tweak it slightly. For example you can join games that have already started but only after a time period of 1 or 2 minutes of the game beginning then locking the game from players joining after this. This would give you more of a chance of pulling a game back and still gives searchers more options of games not entirely slowing the searching times down. Also, I would like to see how this effects searching when "higher skill" is released as then it will surely annoy a massive percent of the community.
Personally, I believe this is a lazy solution to "host hooters" by adding players on if a player is booted but that's just my opinion, I could be wrong.