Linux is not an operating system, its the bit underneath the OS, the kernel. A linux based Os. The correct term is: GNU/Linunx, that being the kernel (linux) and the tools to make the computer do stuff, GNU apps.
Generally, a suite of apps is available to install. Installing these apps, (packages) is very easy. The software packages available from repositories (places the packages are kept) are nearly always 100% legit & safe. If you stick to the standard repositories a distribution provides, (distribution means a version of gnu/linux), you dont have to worry about virus's at all. Your customers will be able to open a package manager, such a synaptic, search for 'itunes' and install a ipod compatible itunes type app with ease.
gnu/linux distributions are usually very secure. If a security issue is found, a patch will usually be written and made available very quicky.
Thats a sort of general jist.
As for the comparison with windows, I personally much prefer gnu/linux. I watch tv, listen to music, write software, download stuff etc... everyday without issue or concern.