Hey,
For me it is the Lack of Hardware and Software Support, For example when trying to install Printers, modems etc. it is very difficult because All the Drivers for the hardware are made for WINDOWS. Software delevopers think "Well No body uses Linux, so why bother" this of couse is compleate and utter crap
Another thing that ties in with the above point is that it is very hard to find someone who actually will come out and help trobleshoot the OS. When I say Oh I need to learn how to do webpages or Commandline stuff or whatever and say I am using Linux IT Pros are like "using linux is pointless, if you say to an employer you can do such and such, they present you with a windows OS, and you say I only Know how to do it in Linux, they won't hire you" this what I was told
This is crap, because webpage coding is supposed to be universal anyways (unless you use Frontpage) and so is commandline most of the time (same Fundamentals)
It's going to be a real learning curve for them, when Linux becomes the base OS in the World and then these people who said it would never happen will be buggered....
Jake