Nvidia have some of the best Linux graphics card support around, ATM, but their chipset support is just garbage, in every OS. You should go read some of the incredible piles of BS folks like Alex V.K. (Motherboard Monitor developer) had to go through to get even basic info on NF2.
ATI is catching up fast on the Linux side of things, though. They've gone from junk to a very usable driver already, and my NDA should show up soon for the Catalyst Linux betas.
They ought to go a long way to dethroning NV in Linux, I'm looking forward to a possible R420 around Xmas time. We even have the new ATI Linux project lead on IRC some times.
While I'd recommend NV cards to Linux people, still, I wouldn't recommend NV mobos. They're just too much trouble, still.... The NV NIC is supported only by a binary, which will never be in a default kernel, and needs constant patching and updating to stay usable... The sound is *barely* working.. 2.0 and analog output isn't too hard, but 5.1 and digital output are a lot of work, and we'll never get Dolby Digital... Not ever... The chipset isn't fully supported, even now, more than a year after it's release... I wouldn't recommend it to anyone, though it's still just about the best K7 chipset around.
Glad to hear logical partitions worked out for ya. I always use them, since you can always put in more.
Anyways, next time you need a new mobo, go AMD or Intel chipset. Via's too unstable, SiS has issues with opening specs, ALi just sucks, but AMD and Intel both open their specs in a wonderful way. My i875P board is supported perfectly, mere months after it's release, and my NF2 will probably need another year to hammer out the last few ACPI/APIC/NIC/AGP bugs... No bariner, IMO.
Luck, and welcome to the Gentoo fold. I've been Gentooing since 0.9 and still loving it.