The revelation that the producers consider Nightwing the holy grail of DC characters that they'd want for an appearance on the show. Whilst it's unlikely that it'll happen due to the Batman/Superman movie and Gotham, much like the The Dark Knight Trilogy keeping Bruce Wayne out of Smallville, that the producers want the character to appear was a source of rejoicing for fans.
Felicity, Slade and Roy becoming series regulars in Season 2.
The Flash series that will spin out of this show.
Better yet Three Ghosts ends with Barry getting his powers after being struck by lightning from the particle accelerator and falling into a bunch of chemicals.
Even better, after the series was confirmed to go to series, Stephen Amell announced he'll be appearing in the pilot.
The announcement that Summer Glau would be cast in season 2. Many are happy about this, although some are cautiously optimistic, given the 'Summer Glau Curse' and all.
Oliver taking up a Thou Shalt Not Kill policy pleased a lot of fans, especially those who didn't like his portrayal in the initial Huntress episode.
The implication in season 2's first episode that Ollie will start calling himself Green Arrow has a lot of people pleased.
Amanda Waller got squees when she was announced, but when she approaches Ben Turner, offering to put him in a squad that she's forming, nerdgasms resulted at the prospect of the Suicide Squad appearing on the show.