For stills, lightwave's full blown go-and-have-a-long-meal-render version of DOF has always been the most natural. It fell apart however with animation and there were visible artifacts that popped in and out.
AE's camera blur is just a blur. It tries, but you don't get any bokeh, but then you don't get any bokeh really really fast.
While the Nuke plug in version seems nice at the outset, I've found lots of scenes where it creates an almost vector look to thinks - too sharp or something. The bokeh becomes disks far to easily. This is great for makeup ads but not much else.
Lens Care Seems to bridge the gap nicely between being realistic and fast enough. (is anything every truly fast enough?) And its also a personal preference issue. Some people like the look of a leica lens and some people like the look of big-glass pentax's - so what is "realistic" to you?
And with the controls available in Lens Care and the custom iris (try a high contrast dandelion puff - it creates gorgeous bokeh!) you can really zero in on the ethereal.
Its not as fast as I would like (especially at higher bit depths and large frame sizes) but I find the wait worth it.