They are still extremely popular and as long as you buy a high end one and not a cheap placebo, they do their job well.
There are a few threads on this in the forums, and if you need help installing, send me a PM. I used the Mirror tap kit, as I've ran one for a long time and it's from a reputable company.
Unless you really want to use the Smart cord (or similar) I see no reason to run a long cord and then mount a switch and tap the fuse box.
I was interested in the gen5diy kit, and someone on here ended up using one, but I've heard of a lot of failures from some of their harnesses, so it scared me off a little.