I actually really like what they did with her. The fact that she can heal more often, but has to monitor her own health, is just awesome. Coupled with the fact that she can sustain herself with a harass ability (yes, I do consider this harass, because a smart enemy vs a smart Soraka WILL be zoned by it to deny her sustain) makes her a champion that actually requires skill. I'm not implying that the old Soraka required none, but it was easy to be a brainless sustain bot, with nothing to worry about but mana, and actually be effective. Now, she's rewarded directly for zoning and landing her skillshot with the ability to provide her partner more sustain.
The one thing I miss, however, was her ability to grant armor to an ally. I still sometimes find my self preemptively popping a heal when my ADC goes to trade or is being focused. The mana, I could take or leave. I can understand why it was removed, because it allows her ally to constantly spam abilities, which are designed to be gated by mana, without building the appropriate items. However, it's on such a high cooldown now, that I can imagine it having this alternate use without it being too unfair.
I'm going to be completely honest-- I liked the old Soraka a lot more. But I think the way they chose to rework her was incredibly smart.