Another system that has an "interesting" setup is HP-UX 9.x, which has an 
/etc/rc that calls on a number of other scripts that are relatively 
self-contained.  They have silly names, but the concept is good:

/etc/netlinkrc	# start up the network interface
/etc/netbsdsrc  # start up low-level daemons, e.g. routed, named
/etc/netnfsrc   # start up nfs server, client daemons
/etc/netnfsrc2  # nfs mounts, automount

There are others, but one nice thing about this is that the scripts know 
how to shutdown and restart the various daemons if you simply execute 
them again.  At least, they're supposed to; there are limitations that 
don't need to be delved into here.

I only bring this up to point out that at least one commercial vendor 
chose not to embrace the svr4 way of things (there are no run levels in 
9.x, either) but still managed to split things up into manageable 
chunks.  That's not to say I prefer it; myself, having /etc/rc.local and 
/etc/netstart is far more than enough.  Local policy dictates adding 
a few lines to /etc/rc.local to check for a startup file in an 
nfs-mounted directory with any additional commands (hey, if the server
farm is down, they're not going to get any work done anyway ;-).

--scott