Ive never used the EO ruleset before, so I have no experience with it, but the one published by WD (I think) and available for dl at GW website did fine when I was playtesting Harlies [was thinking about getting them before deciding on DE (might still)]
As for atmosphere I played them as a friendly game, as the Codex for them is outdated and high-priced. My opponents reaction was "wtf?" When I had my Jesters teleporting around and my GH and Solitare running havoc in their ranks, but that was back in 4th when you could consolidate into another unit for CC. Today I would probably field a different make-up, but all in all they are a fun army to play none the less.
While the Harlies worked wonders for me in the play tests, I saw them as one-trick ponies. CC mastery yes, but once they fought them acouple of times my opponents were coming up with cleaver ways of stopping them in their tracks. I did like the solitary DJs teleporting around, but I just couldnt bring enough anti-tank to the field without having to resort to melta pistols, which disapointed me heavily.