[edit: there were some inaccuracies with the decision criteria of these videos. Joseph is reworking the analysis and I believe will post an updated video. Stay tuned!]
I inquired about the iSight method in the comments and Joseph was kind enough to run the numbers 
Good stuff! I've been happy with the Keith Count, but iSight seems worth a try.
So, I ended up choosing Isight because I (an impressionable new player) heard some people on stream talk about it being newer and better (MCG perhaps?) and the article seemed convincing. Additionally, I found the 1/6 multiplier more attractive than the 1/7 of Keith Count. I ended up making some flashcards for the floor(n/6) in the range of interesting pip counts... I guess one could do the same for 1/7?
@davidklausa, do you have any tricks for mentally dividing by 7?
Heled's proposed Pep-Count uses a (much easier) 1/10 
I think I might give it a go for a bit and see how I like it.
I was under the impression that iSight is a little more accurate but quite a bit harder to learn and use. Maybe I'm just biased because I'm already good at Keith and didn't see enough reason to change. But if I was starting fresh, iSight is probably best. It does seem easier to divide by 6 than by 7. I don't have any tricks for dividing by 7, but it's like my Half-Crossover pip counting: You use the same numbers so often that you just get used to them. When I was learning both of those I did similar to what you did with flash cards: wrote out a list of all multiples of 3 (for pip counting) and 7 (for Keith). Also, the private school I attended as a kid endlessly drilled us on multiplication charts so I had a solid foundation.
And now there might be a new contender to join the Counts pantheon? Let us know how the Pep-Count goes!
Isight has a traditional decision criteria a la existing adjusted counts but also a way to get to cubeless probability estimates. This advanced mode adds difficulty but lets you theoretically make match score adjustments more precisely.
I am on easy mode...