Splitting of ephemeral data seems to have a benefit, the rest seems more like rather noisy busywork to me.
People accidentally blowing away pg_clog or pg_xlog is a pretty common occurrence, and I don't think there's all that many tools that reference them. I think it's well worth renaming them.
Pretty sure every single backup tool or script out there is referencing pg_xlog. If it's not, then it's broken...
