Her buffs were good. I tried her at release and didn't play her after 3 games or so because she was feeling subpar. After these buffs, I'll probably be playing her quite a bit over the next few days. The mana reduc on her Q keeps her from going totally OOM, the range increase on her W makes it so that you're not in gap-close range to use it, the range increase on her E makes it useful, and her ult still wrecks people.
As far as building her, to me, it still feels like she does better with tanky MPen CDR. I build:
From here, I complete Abyssal or Rylai's, depending on whether I need O or D. I should also work a Haunting Guise in here somewhere, as that is also tanky+MPen
TL;DR - Buffs made Syndra pretty good, build Tanky MPen CDR