There are some boards with nForce3-150 already being sold, and some with nForce3-250 may be out now. I have the 150 chipset. It has single-channel memory, and memory bandwidth is similar to nForce2 with dual-channel. I got the Chaintech ZNF3-150 board because it has AGP frequency lock and it works well with Mushkin PC3500 Level II RAM (which I already had). I also got an A64 3200+ at the same time, and it's running at 10*220 (multiplier locked at 10) with 1.520v core and 2.75v dimm, memory timings 2-3-3-7. It's a nice improvement over the Abit NF7 and mobile 2400+ at 2200 that I had before.
From what I've read, the VIA boards score a little better than nForce3, but they don't have AGP lock.