Fast labors are just genetic for me, apparently. My mom and sister both had 4-5 hour labors with their first. My mom then had 2.5 hours with the 2nd, and 1.5 hours with the third (ME!). I followed this pattern by having a 2.5 hour labor with a preemie, where my water had broken 4 days earlier. I'm not expecting my 2nd one to be faster than that if full term, but I'm not discounting the possibility either. I'm guessing I'll probably do about 2.5 hours again, but we'll see.
Anyway... for me, I was on contraction monitors all day. I was not in labor until 5pm when I felt that first little contraction (which felt kind of like a gas pain that moves). It wasn't just a tightening. It actually hurt right away, but I could still talk and eat and all that fun stuff. I ate dinner while having those contractions. Within the hour, they were getting alot more serious, and I needed to hold DH's hand (I was stuck in bed, so no changing positions except to lay on my left side and relax, a la Bradley Method, which we'd had a crash course in that afternoon

). 2 hours after the first contraction, I hit transition and the nurses checked me and baby was "right there", so they raced me to the LDR, where I then had to wait for an OB to get there, etc. So it was about 15 minutes before I was "allowed" to push, and then I pushed 3 times and DS was out.
Yes, some women have really light early labor for a long time and then have a fast active labor, but some women jump right into active labor and get it over with right away. My family is apparently in the 2nd camp. I really didn't mind my labor, although it kind of makes it hard to get a grasp on it when thinking about it after the fact. Like it's hard to remember how it was because it just zoomed by and was done. But since I was laboring in bed and told to use a bed pan for urine, even though my body was screaming to get upright (and I didn't know any better to challenge them on all this, due to my situation of why I was there in the first place), I'm glad I had a fast labor. It kept me from giving in to drugs or even being offered drugs until the last minute (and if I'd said yes, I don't think they'd have had time to get the drugs in anyway, but they did offer and DH said no for me, which helped me realize that I was at the "I can't do it anymore" phase and thus it was almost over).
The nurses thought I'd be a while because I was a first time mom, so they just left me alone. I was the talk of the L&D floor the next morning!

It was a wild ride from the antepartum unit to the LDR.