I spent Friday downloading the last three volume's worth of One Piece and re-read the fights in full; I must say, Enies Lobby had a lot of glorious battles.
However, the subject of this topic is indeed Gear 2: I noticed upon my second read that the Luffy v. Lucci fight wasn't nearly as close as people were saying. Luffy and Lucci were pretty even before Lucci transformed into his Man-Beast form; after his metaphorphosis, Lucci seemed in control but not dominating the battle.
However, once Luffy used Gear 2, he was beating the snot out of Lucci until the doping wore off; this goes for both instances, prior to Gear 3 and after it as well. In the final bout of the fight when Lucci used his more agile Kamie Bushin, Luffy was still dominating the fight until Lucci pulled out the three Rokuougan, which evened out the match a bit.
As such, I think that had Lucci not possessed that Rokushiki Hiken, he would have been beaten down fairly decisively; not quite as one-sided as Luffy v. Blueno, but enough to show a major distinction with Luffy's new form. The Luffy v. Lucci battle reminded me a lot of Goku v. The Demon King Piccolo II, where Goku was clearly more powerful than the latter but Piccolo got in a couple lucky shots that disabled Goku enough to give him the edge in the battle (though Piccolo ultimately lost).
That being said, what do you lot think of Gear 2's appearences later in the manga? Lucci mentioned it's a life-decaying technique, but I could easily see it being used against the next bosses, provided the bosses are physical fighters (against Whitebeard it seems like a certainty).