Devil's advocate here, since I'm going to say the opposite of what I actually did myself:
I wouldn't recommend the original H2O in the specific case of someone coming from a PW2+.
Sure, the screen is larger and evenly lit, but the hardware was a generation behind Amazon at that point, so, the CPU is slower (okay, not a deal breaker), and more importantly, the eInk controller was also a generation behind, aaaaaaand, it shows. It'll never be as snappy as a PW2+, no matter what you do with it.
That said, that's exactly what I did: moved from a PW2 to an H2O. And I survived

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But, the Forma is infinitely more pleasant to work with.
On the other hand, the latest H2OČ *should* have a similar hardware (not *quite* sure as far as the EPDC is concerned, though). Otherwise it's Clara/Forma for a sure bet on that front.