My first baby was a girl and I had classic "all day sickness" until I hit my second trimester. Lots of vomiting-- to the point where I planned my meals based on how they would taste coming back up.
My second baby was also a girl. I had nausea with her during the first trimester, but no vomiting. (Aside from one time when I thought Long John Silver's would be a good idea.)
I think the difference came down to age for me. I was 17/18 when I was pregnant with my first, and 23 when I was pregnant with my second. I think I just had too many hormones the first time around becaus I was so young. I came to this conclusion after talking to a couple other people who had kids further apart. Not exactly sound science, but I'm no scientist. LOL
I'm not very far along into this pregnancy, but I've had some serious spells of nausea. I don't remember it this early on before, though I didn't find out I was pregnant with either girl until I was between 6-7 weeks, so who knows.