If you still play 3e, which other mechanics (if any) have you imported into your game?
None whatsoever. But several of the 'new' features found in 4e are also found in my house rules, going back in some cases years prior to 4e's release.
'Minions' (different from the 4e model, but serving a similar purpose; min. HP and several other weaknesses compared with the standard), 'Elite' monsters (different again; max. HP and several other strengths), 'Channel Divinity' (called the exact same thing, but meaning something a little different), Skill Challenges (partly from Unearthed Arcana [Complex Skill Checks] and partly from elsewhere, as well as being of my own making), saves based on two ability scores each (but in my case, the
average of the two, rounding up if one ability in particular is higher in each case, down if the other is), [Spot + Listen] -> Perception, [Hide + Move Silently] -> Stealth, a few other similar or identical skill groupings, 'Bloodied' (but with 4 stages, not 2). . . I seem to remember that there are couple more as well, but that's all I can recall of the 4e rules, that also - coincidentally - more or less match up with some of my long standing house rules for 3e.