Shell scripts are awful for boot. They have no expression of a dependency graph and truly pathetic notions of state. Hell, starting a process in the background takes ACTUAL THOUGHT in a shell script. How insane is that? systemd may not be as thoroughly tested but at least it's designed thoughtfully and will eventually be more reliable. For now, let it be relegated to arch and let them test it. What are you even doing with arch on a server anyway?
inssrv adds the dependency graph you're looking for.
Standard on wheezy. Allows for parallel launch of services.
I'll spend more time in hardware init (especially on servers) and fsck (even just journal replays) than service startups for most part. Even my servers (minimal services starting) take a while to come live, mostly due to the actual workload stack coming up. Then caches get to warm up and all that jazz.
