Though I challenge anyone to use Linux as their main OS and never have to go under the bonnet.
I use Ubuntu daily at the office by choice. I haven't had to go under the bonnet for anything. I am using a Dell Latitude D630 and everything just works. Now if "under the bonnet" means installing apps via the command line versus the GUI then yes I have.. it's faster to type "sudo apt-get install xxxx" than to have to wade around in the GUI. However, this is not a necessity.
With that said, my computer at home is a MacBook Pro. Though I think my next computer will be a Dell Latitude of some sort with Ubuntu. I would rather save $600-700 and get a faster machine.