I had a 2.0 that I overclocked for a while. I was working at a computer store at the time, so I kept checking inbound CPUs until I found one with the stepping that was confirmed as a Northwood that overclocks well. I think I had it running stable at 2.8 or something like that. I did all the things you're supposed to do to ensure a good overclock... watercooled it, properly lapped the copper heatsink, replaced all the LEDs in my drives and front panel with blue ones so the green and amber light wouldn't interfere with the higher FSB frequency, added CCL lighting to prevent the electrons from having to find their way in the dark, and took a jigsaw to my case so I could install an acrylic window that would let all the pesky photons out that might collide with the electrons. Pretty sure that last thing gave me another 200MHz.
A buddy of mine with far more devotion bought a Northwood 1.6, IIRC, and had it cranked to 3.0 with the aid of a Peltier cooler. He left work an AMD fan, skeptical, with new motherboard and CPU boxes tucked under one arm (just to prove his point, of course), and came back the next day preaching the Pentium 4 gospel.