I find that dictionaries and products alike should be very important. On some sense it is even more important to commentaries (at least not less important than it).
But when I want to buy a dictionary, I actually don't know which to buy. NIDNTT/NIDOTT, BDAG, HALOT, TDNT, etc. seems very good. But which one to pick?
So I think that there is a need of a product guide on this. Similar to that of Commentaries, S, P, L symbols will also helps a lot.