So, I've finally decided to get this thing off the ground! I'm going to offer reviews of the various pre-packaged natto varieties I've tried.
Let's start with one of my favorites so far...
Goku Kotsubu Mini 3 seems to be a fairly popular brand (read: I've found it in more than one store among the few that sell natto). The beans have a nice texture and richness, and this type comes with a seasoning pack and some mustard. The sauce is a little darker and more flavorful than some others, which I like.
The meal pictured in my first post was made with this type of natto. The beans here are a good size and as far as their "stringy-ness", they're about in the middle of the pack. The long, stretchy strings formed by natto when stirred are supposedly a key part of their flavor- the more strings, the more pungent and "fermented" they taste. It's important to stir natto well, preferably with a little soy sauce or the sauce provided, to loosen them up and release their full flavor.