General thoughts and preferences, what I've picked up so far basically.
Starting from the top. Oval handle not too stiff with 1,5 (fish scale) grips.
Middling at the bottom. Spine through to the toe (or at least some meat there). I'm not one to actively look to smack one from the toe but it's nice not to have to look down nervously if it was duck bill toed.
Ending in the middle. Grains, grading on looks, not too many and minimal amount of 6ish. If for not other reasons that too many will mean too expensive and too few means it looks cheap. Any knots,stains etc in the playing area might effect the feel of a bat but probably not the performance.
At the moment I'm looking for a mix of my CA and my Lekka Big Hitter.
In saying all of this I think I can tell you which bats I prefer. A bat maker can tell you why.
Really impressed with a team-mates Redback Sunfire btw.