Post-U15, Imp Feint doesn't have an "absurdly long" animation - it looks just like a normal atk AFAICT - but there seems to be a delay between when you use IF and when the Bluff effect procs; and unfortunately, it also seems like if you attack before it procs, you interrupt the feint and no Bluff effect happens.
![Frown](/forums/images/smilies/frown.png)
So what I have to do is hit Imp Feint, wait for the Bluff effect to proc (you'll see the icon show up over your targets' heads), then attack; haven't figured out exactly how long it takes for the effect to proc, though.
That said, I can't see adding CE+IF to the average pure rogue build because of the feat cost. The rogue I'm using it on is actually a staff-wielding Ninja / Acrobat; I'm using IF so I can get SAs on my Cleaves vs mobs.