It could be your trackpad settings. I've got mine set up with tracking speed right in the middle (5) and two finger scrolling 'scrolling speed' set at 2, on the slow side. I find it works great.
Edit - added this paragraph last: In Firefox, preferences, advanced... check "use smooth scrolling." It makes it much smoother, and is my default setting for FF. With two-finger scrolling on the MBP it is pretty interesting using my settings... and I really like it. The scrolling has a bit of a 'bounce' in it, like the iPhone. A faster flick, and it scrolls on for a bit, up or down - a bit of an 'overshoot.' With practice it actually is addicting. As the page is gliding down after a nice fast flick, you can then stop it instantly with a two-finger tap on the trackpad. It feels very fluid.
Several things I notice... as I move my finger on the trackpad, say in a circle, if I accelerate my motion the on screen 'circle' gets bigger, or when moving diagonally or horizontally across the screen. So, when I 'swipe' my finger across the screen, the cursor slides across the whole screen with ease, yet when I move more deliberately, it is uncannily accurate, feels like an extension of my finger. I think the mid-point tracking speed give a great overall 'feel' on the trackpad, both for reach and control. On the 2-finger scrolling, I find the slower setting (2) seems to be easy to control. Like I said, in Safari it's almost like I'm actually sliding the web page with my finger, it's that smooth, even when slow. FF is a tiny bit more jumpy, but still relatively smooth. In FF, and even in other apps, depending on how sensitive they are to scrolling, I can 'flick' with two fingers up or down, and the page will scroll a bit longer, before stopping, as if it has some momentum (kind of like the iPhone does.) With a bit of practice, this becomes natural, and I'm scrolling and clicking and pointing and all the rest with very natural little flicks and very light touches. Much superior to anything on the Windows side of things.
By enabling exposé in a lower-left hot corner, and widgets in the lower-right hot corner, with a simple flick/slide of my finger I can enable either one just as easily as the new 4-finger swipe. No looking required, it's a natural as anything, especially since you can set up whichever corner works with the most natural 'flick' of a single finger depending on whether you're right or left handed. I'm not sure if I'm really ready for an "improvement" on what for me is already the ideal trackpad on the MBP classic. But, I have to assume once you get used to it, it also is pretty amazing... but I don't know yet since I've not played with one.
