I really hate this kind of generalization. :
Linux is "ready" for my desktop and has been for over a year now. I honestly feel somewhat limited at work when I have to use Win2K and Word, for example. I can do everything I want and need with Linux and do it better than I can in Windows.
But, if I were a hardcore gamer, then no. If I were a hardcore AutoCAD user, then no. If I were dependent on M$ Office, then, well, maybe. If I were a graphic designer, then no, but, as pointed out in The Register, I'd be using a Mac.
Linux is a better server OS than Windows and always has been. It is a better programing worktation or scientific workstation OS than Windows.
And for the average home user who wants to surf the net, get e-mail and maybe write simple documents, I'd say linux is ready. Depends on the user.
So, yes, Linux is ready for the desktop, as long as the user is ready for Linux.