It depends on your skill level and where you play her.
- She's flat out stronger as a solo laner than she used to be, to the point of being a strong anti-melee pick thanks to her sustain, poke, and disengage. Definitely viable top, although I'd hesitate to take her mid due to her lack of burst counter and relatively short range.
- She's basically useless if you can't land her Q. If you don't land your Q as Soraka, you're less useful than a Blitz that can't land his hooks. It's that big of a deal.
- If you're good at landing your Q, then she's not too different from before.
- Her base healing and sustain are down in exchange for better AP scaling. You can't skate through to midgame building support and utility items any more; you NEED to get raw AP to function. The flipside is that if she gets ahead, she does better than she used to.
- Her utility is stronger. Better slow, better secondary effects on her W thanks to Rejuvenation.
All in all, I think that by and large they succeeded in giving her windows of vulnerability. The problem is that they're A. very predictable, and B. she doesn't have any options except to take them. She can't "play safe" any more because of how reliant she is on her Q to sustain her lane partner, and all of her "save me from the dive" tools except her ult have been removed. She no longer gets burst healing from her Q and it doesn't scale with targets hit, so if you catch her - ever - she's dead.
IMO, if they want to give a support champs as many mandatory windows of vulnerability as Soraka has, they need to make it less lethal to expose them.