Correct... revised ATA controller is the only real difference. The 1st revision had issues with corrupting data when using HDD's larger than 10Gb on the primary IDE bus, and/or running a slave drive. Whether you will experience this issue with a rev.1, and how severe it will be varies from computer to computer and HDD to HDD. My 450 was purchased as a 300mhz Rev.1 initially and I ran a 40Gb Seagate drive and a 10Gb Seagate on the internal primary bus, and ran the corruption tester and it came up with zero errors... conversely the other one I have was originally also a 300 rev.1 and we put a 120Gb WD drive in it and it was writing errors here there and everywhere. I elected to buy a Rev.2 board for mine anyway however, just to be safe and make sure I'd never have problems, and put in a 450mhz CPU and a rev.2 graphics card, which is slightly faster than the rev.1 card and is identified by the presence of a small black finnned heatsink on the GPU which is absent on the slower card.

Also as an aside, the way to tell a Rev.2 logic board visually is by looking at the 'CMD' branded chip in the corner of the board near the bottom PCI slot. If it has the suffix '402' then it is a Rev.2 board, if not it is a Rev.1.