i would generally let customers chime off routers which are strat 2 or 3. if a customer has other needs, then they can deal. if they are really concerned, they should not bet on me anyway.
3) If you do have a local NTP server, do you have a standby local NTP server or do you use the internet as your standby server?
I agree. Someone downstream from you who is *really* concerned about time can either do it themselves or pay you to do it. If you are just date stamping logfiles, you are probably better off running a few servers that sync up externally to one of the free pools (http://www.pool.ntp.org/en/ ) in your region (they generally round-robin IPs to several different servers) and sync your internal stuff to your internal servers. The main reason for that is that the "free" servers won't remain "free" if every single individual host on the Internet is hitting them. By running your own internal servers a stratum down you offload that traffic from the public servers and preserve that resource. NTP is a great candidate for v4 anycast, too, so you can have a common configuration at all your locations if you want.