It may seem as if there is a choice between using the ProtoManager or this one, but there actually isn't as you should use both. I find myself doing that very regularly. Cubik's proto reader is very good for browsing and scrolling through all available items (which is a feature that can't be valued highly enough for game-design) while the ProtoManager allows side by side comparisons by opening various windows (which is also very useful).
Quality wise they are both on the same level, at least I haven't run into any issues yet.
Anyway, I wouldn't want to miss either of these readers, they are both pretty useful.