A few thoughts:
-Overrun: This is a fun mode and much better than Beast mode from G3. The maps all seem good and a few look amazing for 360. OR really shines when your team knows what to do, so it'll take the community some time to adjust.
-Survival: Haven't played it yet.
-TDM/FFA: It's very fun, but it isn't really Gears. It kinda looks and feels like Gears at first...but there isn't any of that push and pull team work than the prior games had. Map control doesn't matter much. Standoffs don't happen. So, it isn't really Gears. It's still very fun for what it is though. It's very run and gun and you're almost always on the move. The maps are all square shaped with many different interweaving paths. I haven't been 2-pieced yet so i don't have those complaints. Wall bouncing still exists somewhat, but it's less effective since everything is faster by default. The gunplay is MUCH more consistent. I think part of this is due to the removal of the Active Reload damage boost...making fights feel more reliable and allowing the player to judge how many shots do how much damage and whether they should "fight or flee". Dropping from ledges feels amazing and may be the single best addition. Overall, the game is just fluid and fun....but less strategic than the Gears before it. Not bad for a spin-off...(it better be a spin-off).
-Campaign: Only finished Act 1. Looks amazing. Writing is kinda bad, even for Gears. Not much character development or story stuff so far. Again, the game is very fluid and fun, but without the story hooks it's kind of mindless. Declassified stuff is front and center and i don't even know why anyone wouldn't activate them. I thought they were side areas...but they're basically campaign scoring modifiers for upcoming sections. Feels arcadey and fun, but somewhat inconsequential story-wise.
Overall: I'm glad it's not a rehash and this is a good time to try some new ideas with the series. What they have is very fun, but not fully the Gears i love. I would like to see some of these ideas tied into the mainline games, but for now, i'll enjoy Judgment for the mindless fun that it is.