I'm using the ABF layout, and I cannot get target buffs or debuffs to display. They display just fine on the player frame, though. It doesn't work for friendly or unfriendly targets; doesn't display my PW: Fortitude buff if I target myself, or the mob's SW: Pain debuff in combat. Debuff highlighting does work if I have it enabled.
Make sure your Auras in the Target frame are not set to Hidden.
It was not, but I inadvertently found the problem when I checked that. =)
My target (and target's target) frame, while certainly looking like they were using the ABF layout (identical to the player frame, in other words), didn't actually have any layout selected. I clicked ABF on both and the buffs magically appeared. So thanks!