I got the free e-mails and actually printed them out and keep them in a binder with other interesting interviews and essays (Rickson, Roy Harris memoirs, etc.) on jiu jitsu.
I think the biggest takeaway from LI is specialization. He has a nice e-mail/essay where he talks about watching tape with his instructor years ago. The tape was full of all the people we know and love as champions of jiu jitsu. The difference was these were tapes of all these guys competing as blue belts and purple belts.
What LI thought was interesting was seeing the same moves that these guys have mastered as black belts, still being developed as lower belts. His point was that if you want to compete against the best, you need to develop a go-to submission, a go-to sweep, a go-to throw or takedown and work them until you have truly mastered not only the moves, but how to set up and re-counter.
Other areas of your game may become terrible (or average, given the amount of training time this approach requires). Don't worry about that. Just focus on those 2, 3, or 4 submissions/sweeps/throws that you'll be doing for the rest of your life.
I don't follow the gameplan. But I am spending at least half the training week just focusing on what I've decided are my best submissions and sweeps.
There's more to it, some sports psychology that isn't half bad. But the theory on specialization is what really impressed me. You see it all the time in pro sports: guys have their shot or their pitch or their move. LI just brings that thinking to jiu jitsu training.