For the average user, who needs all the GUI bells and whistles, I'd say that KDE4 probably represents the best option right now. Gnome 2 (which PCBSD currently includes) is no longer supported, and Gnome 3 is still going undergoing growing pains since its last major revision, whereas KDE4 has "settled" into a very stable, usable desktop environment (from my experience, at least).
LXDE is also fine, but it is intended to be a more "stripped down" DE as compared to Gnome or KDE. This is great for older hardware, but again, for all the bells and whistles you'll want to use either Gnome or KDE.
Of course, if efficiency is what you care about, then getting to grips with the command-line, and/or window-managers like Stumpwm, Ratpoison, Scrotwm, etc. is the way to go. But not everyone has the time or patience to surmount the learning curve involved.