I feel like a lot of our posts are along the same lines: what happened to my nice little baby???
Same thing is happening here in the Z household. Alexander is waking up at his usual 3 or 4 am, but instead of sucking down a bottle and going back to sleep until 7, he is completely awake and ready to play. He screams when we put him back in the crib. When he was still a little sick last week, we let him sleep with us, because his coughing was so bad. Now, I don't know if he got used to that or what, but he screams until we bring him in bed with us. Yesterday, I was like, ok, he is completely better, he should CIO, extinction style. But after an hour of straight screaming, my husband couldn't take it anymore and went and got him.
So any suggestions? Is this likely a phase that I can wait out or do I have to make the real CIO effort?

Re: Are all of our babies cranky non-sleepers now?
Mine is not, but JUUUUUST started STTN the night this past week, so don't get jealous!
We've had those kinds of times too- waking up at 4am ready to go for the day!! We usually let him cry for a bit, then just get up with him. It seems to go along with motor skills milestones- crawling, sitting. Is your DS working on walking or anything??
GL! It's so frustrating!
Interesting...he could be working on standing alone and walking. He seems to be getting slightly more adventurous in his cruising.
P sleeps everywhere but here. (You can see my FFFC for that one.) Now that we've adjusted her schedule to what works everywhere else, she seems fine. lol.
I bet A is working on his skillz. And possibly a growth spurt to boot. GL mama!