It depends what you mean by 'desktop replacement' and 'everyman'... I'm a programmer, I use FreeBSD at home, and it's great for development. It's also pretty good for multimedia, for example I now much prefer Amarok to iTunes.
The only downside is that a few things are ridiculously difficult when (in my opinion) they shouldn't be, for example setting up printers.
I don't think the average 'man in the street' could install FreeBSD as a Windows replacement, but then they couldn't administer Windows properly either.
I use FreeBSD on my desktop, and years of hardware problems has taught me to be very selective in the hardware that I buy.
For example, I only buy networked printers that support Postscript, such as many HP or Kyocera models. Then one line in /etc/printcap is all that is needed to be away and printing.
Similar story for networking devices, RAID cards, etc... you buy the ones you that are reputed to work well and avoid the others..
