I've been using this for many years now and am about to replace it because the old one is starting to disintegrate.  You don't always need to "get all technical" to catch trout, but when I'm not getting any interest on stand by attractor patterns I slip this over the net and start dipping to see what the fish in that section of stream are looking at.  I certainly don't know the technical names of the bugs I see, but I know enought to match their size, shape, and whether to dead-drift or tightline and whether or not to give it action.  This little net typically gives me the best advice about what to use and often comes up with some surprising "recommendations".  This net is more important to me than any recommendation on go-to flies.   Let me just say you learn a lot from it, and this has definitely helped me catch more fish than just about any other piece of gear I own.  I definitely find more variety in the net than I do just flipping rocks.

Check them out at:

http://www.anglingdesigns.com/intro.asp