I don't think the command line is an issue. I don't think instructing a user to open a terminal and issue commands is any harder than having them open regedit and add obscure keys.
The really sweet spot is a well designed GUI configuration utility which allows you to generate approriate command line scripts to allow the configuration to be duplicated. Unfortunately, this is rare in the Unix world and non-existent in Windows.
Compared to GUIs, command line interfaces are stable. I am still using commands for 20+ years ago to adminster modern systems, while the recent "upgrade" to Win7/2008 has made so many changes to the interface that it seems like I have to relearn it each time I use it.
Pinging google.com [126.96.36.199] with 32 bytes of data:
Reply from 188.8.131.52: bytes=32 time=8ms TTL=250
Ping statistics for 184.108.40.206:
Packets: Sent = 1, Received = 1, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 8ms, Maximum = 8ms, Average = 8ms
Unlike Linux, I don't think this has been patched.
I once had a computer which did that, a Commodore 64. I am pretty sure most others at that time were that way too. The whole "store the O/S on a R/W hard drive" was an IBM PC/Microsoft idea, as were viruses.
A ROM based system with Ubuntu or Knoppix would be pretty sweet for surfing teh Interwebs.