It's been my experience with spirited children that there are very big humps at all the halves, but the worst tends to be 3.5 years old. Every child is different of course, but I have definitely found my dd to follow this pattern, though, perhaps a few months ahead. Hopefully you will get a lull at 3! We are at another major hump here at 4.5 and I'm looking forward to the calming effect that 5 supposedly brings for most kids. I've also heard that 2's tend to be a bit harder for boys and 3's for girls, but since my ds isn't 2 yet I can't comment other than to say that 3 was way harder than 2 for my dd. There is a whole other level of sass that emerges.
I've found the same thing. I've been reading "Raising Your Spirited Child," and when she said that about the halves, I realized we've had the same thing here. (I highly recommend that book if you have a spirited kiddo, BTW. It's like an instruction book for handling by DD!) And at 4.5 things are getting interesting again. Three was a lot harder than two, here, too, and four has only been slightly better, really.
Both of my kids seem to be getting a little crazy as I get closer to my due date. My mom isn't going to be able to come spend several weeks with us like last time, and DH is pretty much going straight back to work (although he swears he's going to be only going in for a few hours a day, he has to go), so I'm getting kind of nervous. I'm going to be pretty much on my own from day one.