All of these are valuable, but I think they fall into different categories. Some provide useful, but not overwhelming, abilities; others provide a drastic boost in power; still others add versatility, but at a cost.
For example, Knight of the Weave as a one-level dip can be extremely formidable in, say, an Ultimate Magus build; however, it does require delaying progression of spellcasting in the primary class, so there's a pricetag.
One level of Shadow Adept provides a crapload of goodies for almost no investment. (If you care about the shadow feats, you were going to take Shadow Weave Magic by definition.)
What I'd like to do is separate the wheat from the chaff: pick out the ones that give the most benefit for the least cost.
Tiny nitpick: Warshaper, last I checked, doesn't give the bonuses to stats until level 2. That's not to say that level 1 is a bad dip, since it gives morphic weaponry (which is really limited only by what the DM will tolerate.) I actually consider that more powerful than the stat bonuses.
I'll let the discussion play out a little more, and then we can start sorting these into categories...maybe rank them according to the color system used in a lot of the other handbooks.