Anti-tilt followers - the black GI followers will tilt forward or back. The green ones will tilt forward. I haven't used an orange (newest) one, since I started using Magpul followers.
Magpul followers don't tilt. At all. They just go up and down. They work well in aluminum tubes, but in the Magpul tubes, they are heaven.
All of the GI followers I've used will run ... until they don't. I never had one go wrong in a "situation", but in training, yeah, and one nearly cost me a match stage when it threw up all over in the receiver and tied the gun up. It was a two-gun legal stage, though, so I was cool to draw my pistol a few targets early and finish the stage.
That was the last time I used a GI follower for anything but drills and bumming around at the range. My buddy handed me a couple of mags with Magpul followers to finish the match with, and I was converted. All my "serious" mags have Magpuls in them.
Just since you asked what the deal is with the anti-tilt followers. The orange "new-new" GI followers aren't supposed to tilt, either, but I haven't tried one, so I couldn't say for certain.