The current version of blender has a much better island pack algorithm, which is akin to the add-on you recommended in a previous lesson. If you always want to take the time to place the islands in a layout that makes sense (things on the correct side of the body, related things together, etc), then what's the point of using the island packing functionality?
Or perhaps a better question is: when would you use Pack Islands vs manual placement?
The point is to get the most texel to pixel ratio. Pack Island is a quicker way or sometime a starting point to get the best ratio. Manual placement takes longer and sometimes is the better option. For example: doing a low poly soccer ball. Even with simple colors like black and white, if the islands are rotated at certain angles you will get jagged lines when painting or baking the colors. In this case, I did pack island to get a starting point and then manually go through and rotate the problem areas to get straight 90 or 45 degree angles on the outer edges.
Yeah, I'd say you use pack islands as a starting point and then try manually placing things better. Also when I'm in a super hurry, the job needs to be done within the hour, there is no other choice than to work sloppy, you quickly unwrap automatically and pack islands, don't bother with how it placed them and 5 seconds later you're out from UV'ing.