I think Linux has made great strides in being more user friendly over the past few years. The Linux distro that LinuxMCE installs on/over is a very widely used and user supported friendly distro Kubuntu. linuxMCE/PlutoHome tried making it as simple as possible to get installed and running. The problem is getting the hardware to cooperate with Linux. If you are not a novice or > computer user that is willing to do alot of reading/asking questions/troubleshooting I am not sure if this is right for you. But for what you could do with this setup it is definitely worth the time and trouble it might take to set up (for me at least)
Who knows, with the way things are going alot of the cool Linux projects have been made easier to install and use over the years. (see. KnoppMyth - Asterisk@Home/Trixbox) I think I would like to see one day a cd that came with a distro and LinuxMCE on one disc that any user could drop into his/her core core/hybrid and start the livecd and have an install LinuxMCE on the desktop. Click on the button and it walks you throught the whole install with an anaconda like installer for the distro and LinuxMCE itself and having all of the possible needed (available) drivers already there on the CD that would be installed as hardware is automatically recognized during install.
I have not setup a LinuxMCE system yet. I am still getting the core pieces together. The LinuxMCE google video has provided me the needed boost to get going on this.
The forum here is very helpful. Kubuntu forum is helpful. As far as reading there are a million linux related docs to read. I am not sure there is one that sticks out as a good beginner one to read. You could check out RUTE http://rute.2038bug.com/index.html.gz
I think its a good entry level linux book.
They have made Kubuntu so GUI based and easy is should only be a small learning curve if you are used to MS or Apple OS. If you are reading about Mythtv also check out the telephony part of this MCE Asterisk http://www.voip-info.org/wiki-Asterisk