No, I never had heard of man, cause im not a linux person. I can work with Windows all day long, I actually am a tech and love windows.
Even though man is a terminal command, there is often a GUI version as well. Just like in Windows when you click on help & support, most Linux GUI's have a similar menu item.
I guess what I don't understand is why you think it is so much more difficult for the average user. I'm not talking about repairing, that will take quite a bit more practice and experience. I'm talking about day to day operation. I have never had the need to use the terminal for any "normal" operations. Yes, I've played around in it for the experience, though. But the manual is available in the GUI, as well as options to configure most hardware, install programs, access the file system, do updates, etc.
But, just like Windows, when something goes wrong you might need to use the prompt. Average Windows users are ignorant and scared of the prompt too. To them there is no difference between a linux prompt and a DOS prompt. They will call a professional for support.
I don't see the argument that "Linux is too hard and will never be popular" as having any truth at all. Distros like Mint, Ubuntu, Linspire, etc are just as easy, if not easier to use than Windows. Average users will never have a need for the terminal on it just like they won't with Windows. I think there are two reasons for the lack of wide spread acceptance. One being that it can be confusing to pick a distro because there are so many out there, hence no one company to look at and be comfortable with (ie like microsoft). Two, the availability of software. Sure Linux has thousands of titles that are all free, but people are comfortable with their current software and don't want to give it up, even for similar free options.
I honestly think that you are looking to deep into what you have to do. When I look at a computer, I don't really learn each new program, or have to learn how to use the OS. I guess I just see it differently to most. I see the knowledge I have about computers as concepts, rather than individually knowing how to do or use each program or OS. The concepts stay the same. As long as you don't think too hard about it, you can adapt quickly to anything. The whole "windowed" concept is easily transfered between OSes. As long with the organization of the software and apps installed and their functions. There will always be a type of control panel, there will always be some sort of menu system or program manager, they all have desktops, almost all the control panels apps between OSs are the same or very similar, etc. I really don't see much difference at all between Windows, Linux, Mac, etc in terms of GUI. Sure, some may look better than others, and there are slight differences, but the concepts are all the same.
That being said, everything you know about Windows troubleshooting basically remains the same. The only difference is that you will need different tools, and the commands you use in the terminal will be different than you use in the Command Prompt. You also have a much higher degree of control of the Linux OS vs others. But you don't have to use it, it's there if you want. Your confusing more control and more options with greater difficulty. Just because they are available, doesn't mean you have to learn them.
