The nForce4 platform is a good one whether you choose the nForce4, the nForce4 Ultra or the nForce4 SLI. The fact of the matter is not everyone wants to spend the $150 for a motherboard. Pricewatch has the GA-K8NF-9 available for $116, which is about $30 less than the least expensive nForce4 Ultra and $50 less than the least expensive SLI board. For the upgrader not needing the SATA II or other extra features of the Ultra, a board like the Gigabyte GA-K8NF-9 may fit the bill.
Weaknesses of the board include a less than stellar bundle and performance that was lower than the nForce4 SLI board in every benchmark. Of course, if the performance of the mainstream board was the same as the one for the high-end, there wouldn't be a reason to buy the high-end board ;). In any event, Gigabyte has both an Ultra and an SLI board as well.