1. It isn't clear whether it actually exists in both versions, i.e. "standard" and "plus"
The original version had a lower performance. At some point they switched to the "plus" version with better performance (2x if you believe them). You can still send in the original version and get an upgrade to the plus edition for a small fee.
I think they stop selling the original version, but i never checked if that is true for all distributer channels... get "plus" if you can.
... is it really so good compared to alternative more traditional dynamo ac/dc converters ?
JensD (Forumslader) measured the original version, it did not perform so well (No numbers published, i guess more or less in line with the other commercial ones).
The plus version does indeed work better: hard numbers in german
The one crucial detail is bike light: if your frontlight is on, the harvester more or less stops working. I have a forumslader and while the light does reduce performance, the drop is much less noticeable.