We be trolling.
The characters are interesting. Tsuna is not the typical shounen hero in that he doesn't have a "I will be the best...!" or "I am the best....". Yeah, he's a bit of a loser at first, but he toughens up as the series progress. And even with his powerups, he's never the strongest in his group and he does have to use strategy to fight.
That's one of the few character developments of Reborn.
Plus the action is good, IMO. Kokuyou Arc was great. The Varia Rings Arc is how you do a tournament-like arc, short and not dragged out and it had some fantastic fights. Millefiore has been slow but it's still good especially now.
And this series, other than Eyeshield 21 and Yakitate!! Japan, have a very likable cast and females that's not useless!