PCI latency timer isn't quite what it sounds like... Don't think of it in the same terms as memory latency, of which a higher number will give you better stability at higher speeds.
PCI latency is actually the term given to the number of contigous clocks the current PCI busmaster can assert control over the bus before being preempted off. Higher numbers can mean that bandwidth hungry devices can have more time to get their data moved before having to release the bus; lower numbers can mean a little more bus access for devices that need a lot of sporadic bus time.
Higher numbers can be good for PCI Raid cards and video capture cards but could potentially cause problems for things like soundcards and softnics / softmodems. Lower numbers usually work with everything, but can starve out high-bandwidth PCI bus devices. Using extreme values (lower than 16 or higher than 128) can sometimes cause instability depending on your hardware.
I use 64 and I get better disk throughput and have no issues with my other devices. Numbers greater than 64 seem to give no benefit, and after 128 start causing problems with my onboard sound. Numbers lower than 64 (32 and lower for sure) result in less throughput from my disks without "giving" me any other benefit.
Your results will vary; play with it, benchmark it, run games on it and see what works best for you.