This claim seems a mixture of rumors about the early days of GNU/Linux when the command line was more of a necessity and Windows users' understandable horror of the DOS command line. However, it's not even vaguely true.
GNU/Linux has had adequate desktops for over a decade. Now, the latest version of the GNOME desktop is a close match to anything on Windows, and, with the latest versions, KDE has become one of the most innovative desktops around. Even administrative tools are well-represented on the desktop.
You can use the command line, and many users, especially administrators, prefer to do so because it's often more efficient. But for everyday productivity or administration, whether you use the command line is a matter of preference, not necessity. It's also a much more user-friendly experience than the DOS command line.
What this claim usually means is that common Windows software is unavailable: There's no MS Office, Internet Explorer, or PhotoShop. But even minimal research will reveal equivalents that are more or less a match if you only take the time to learn them.
Nine times out of ten, when someone complains about one of these equivalents (such as The GIMP) or claims that it's not ready for professional use, a little probing reveals that the complainer has not explored the program, or has been stymied by a function having a different name or menu location. Often, the complainer hasn't tried or hasn't tried recently the program they're criticizing.
For general office or productivity use, today GNU/Linux offers a complete solution. Because many free software projects are cross-platform, you may even have used some of the applications on Windows, such as Firefox or OpenOffice.org. The remaining gaps are games or specialty applications such as OCR, and the problem isn't that no alternatives exist so much as that the alternatives are slow to mature.
Until the last few years, usability was often ignored in favor of functionality in GNU/Linux. Considering that basic functionality was still needed, things could hardly be otherwise.
But all the most commonly used applications are now mature and giving usability serious consideration. Many could still do with an interface overhaul, but most are no worse than their Windows equivalents -- and, frankly, anyone who endures a platform in which Outlook or Windows Media Player are considered acceptable applications has no business complaining about the lack of polish in any other platform's applications.
GNU/Linux first received serious attention in the greater technology world during the Dot-com era. Then, lack of support was somewhat of a problem -- at least if you mean traditional support contracts. But, even ten years ago, you could always enter into a support contract with a company like Red Hat.
Now, traditional support options are easier than ever to find. If you don't care to deal with a software vendor that offers a distribution, you should be able to find local support in any major city in Europe or North America.
But there has always been an even better source of information: the mailing lists for community or corporate projects. Although the lists are a different model for support, they are not an inferior one. Not only are there lists free, but those who frequent them tend to respond more quickly and with more detailed help than any paid help I've ever encountered.