Archangel of Thune ended up being a pretty good card and while the Hydra didn't quite live up to its hype, it was a solid card during its time in standard. Slivers never really got anywhere competitively but the most touted in Galerider, Syphon Sliver, Manaweft Sliver and Bonescythe Sliver all proved to be the casual all stars we expected them to be.
The major hit in the set was actually an uncommon called Young Pyromancer. While certainly good in standard, it has become a mainstay in legacy and quite popular in modern. Foil Young Pyromancer rivals foil Archangel of Thune as the most desirable foil in the set. I don't think Wizards realized just how good it was - not broken as Delver of Secrets, but an amazing value engine spitting out tokens is something that can see consistent play forever.
Chandra, Pyromaster had some sweet times in standard and would again with her 2015 reprint. Being a modem playable, she probably won't stay 5 bucks forever. But the real winner of the planeswalkers was Garruk, Caller of Beasts. He takes quite the mana investment, but he proved to be worth it. It's highly unlikely this version of Garruk will be seen again, so he's probably not going to be 5 bucks forever. He's too good in Commander for that.
Cards that haven't aged well include Lifebane Zombie and Xathrid Necromancer. Lifebane was a staple in the sideboard when he was in standard and the Necromancer was the primary engine of some very competitive human decks. The Zombie is under a dollar now and the necromancer is now pretty much bulk.
Another hyped card of the time were Savage Summoning, an instant which had a cool effect but was eventually relegated to the sideboard against control matchups. Imposing Sovereign looked to be a great tempo creature but proved too fragile to live up to how good it looked on paper.
Magic 2014 was deservedly a hit, full of cards that will continue to see competitive play in eternal formats. It also has plenty of casual hits that will keep the overall set value increasing in years to come.