Aww man that's too bad, I really liked that feature, I haven't tried out imessage though yet for fear of it not working. I'm too busy to try to deal with too many iOS 6 problems, I've already had to try and figure out other glitches. Btw I have an iPod touch so it's not like I haven't been texting on my phone just not on my iPod.
Yes the dots in the bubble are still there in 6. And yes all it notifies you of is the app is open and the have the cursor in the text box. I use the read receipt because that way the ppl that I don't care I'm ignoring actually see that I am ignoring them. Lil passive aggressive I guess.