I had my dd at 30 weeks and she came home at 35 weeks. She slept a lot and was super easy as first, but like lanaross, my dd developed really bad reflux about a month later and it was awful. She would cry while spitting up, spitting up SO much like half her bottle or more every time, and constantly grunt and struggle like she was constipated and it broke my heart. I took her to the doctor and they said it was normal. I cried and cried for the next few weeks because she looked like she was in so much pain. I finally went back to the doctor and said this is not okay, I know this is my first but there has to be something you can do. So they finally prescribed Zantac for her reflux and seriously overnight she was a happy again, and was perfectly fine from there on out!
I think we were lucky and I knock on wood because #2 is on the way, but dd was such an easy baby. We kept her NICU routine (eating at the same times, changing diaper before feeding, etc.) until she kind of developed her own, but were always consistent with everything we did. She slept right after every feeding, and we always put her in her crib to sleep. When she woke up she was in a good mood and wanted to play, and it was close to clockwork when she'd be ready for her next meal. When she was awake, she was very alert, and as she got older, she was so smiley and just happy overall. She is 2 now and still is such a great sleeper, loves her crib and I'd say 5/7 nights she has absolutely no problem going down for a nap or going down for the night.
So I guess that's all to say - I don't think it's true that preemies are more high needs than any other baby once they get to their original due date. I'm sure it's all their personality!