The XFree86 nv driver interacts very differently with both the installed graphics hardware and the operating system; if you find it to be stable and don't require features it doesn't offer, there's no reason why you shouldn't use it (aside, possibly, from performance considerations), but the fact that it works (or doesn't work) allows no conclusions to be drawn with respect to the nvidia driver.
Both AGP SBA and FW are frequently causing stability problems, you will want to make sure they are disabled (/proc/driver/nvidia/agp/status), which they are by default. Setting NvAgp to "0" prohibits use of the AGP port; you will want to do this for now. The mem=nopentium kernel parameter was an interim workaround for a Linux kernel bug and is no longer required or even desirable with recent kernels; don't pass the parameter to Linux 2.6 kernels. pci=noacpi disables ACPI PCI IRQ routing, acpi=off disables ACPI support alltogether; if your kernel wasn't configured to feature ACPI support, neither option will modify system behavior. Check /proc/interrupts to determine if an APIC is used; if so, the noapic kernel parameter will disable it.
These are only some of the possible error sources, however, and while I named a few others (fbdev, other hardware problems, ...), you should browse the archives of this and similar forums to get additional suggestions.