Thanks for all the great input. I think I may have found a solution that works for me.

Home Depot

I think this must have been what Brewer was talking about. Galvanized posts cost at least twice as much as wood (and they're not as nice looking), but I like the idea of not having to dig or set posts for a long time. It looks like these will also make the task of replacing the wood later on reasonably easy (assuming the lag screws and bolts on the hardware aren't completely locked up).

I'll have to do a little measuring and head scratching to make sure these will work in my sloped yard, but I think if I "stagger" the rails a bit (more ugliness), I may be able to pull it off. Better make sure before I start buying stuff, I guess.