I'll have been training for three years this January, using 5/3/1 from the start.
When I began training I didn't know it but I was very weak: squat 100kg, bench 85kg, deadlift 135kg, and I can't remember my press but it was around 50kg. My numbers now are not phenomenal but considering how I started I have made a lot of progress: squat 180kg, bench 130kg, deadlift 210kg, and my rep maxes are still progressing every week
I will say that I when I started I probably made all the mistakes jim mentions in his books and articles, I started too heavy, and kept altering the program even though I knew nothing about lifting (it's pretty embarrassing really), But eventually learnt my lesson and fully embraced the philosophy of principles of patiently training with a bigger goal in mind. Ironically the better I have become at training the simpler my programming has been
These days the focus of my training is hitting rep maxes. 2.5kg or one more rep here and there don't seem a lot but it adds up! I know I've read that somewhere before, and it's perhaps even a direct quote from jim, but I have found it to be very true!
I now follow the program as closely as possible. I train in 6 week cycles starting with hypertrophy then increasing the intensity while decreasing the volume over several cycles.
The templates I find most effective for this (for me) are
*Boring but big or triumvirate
*First set last for multiple sets
*Joker sets and first set last for one set.
As strange as it may sound the difference that this training has made to my life is invaluable, and somewhat beyond the scope of this post. I will just say that training hard, with purpose and intensity, carries over to every aspect of life