Well, come friday I will be halfway thru the challenge (6 weeks in). This is my very first experience with the 5/3/1 training style and so far my impression is like this:
The first month (50%) was damn easy, I mean I did not get any DOMS at all in my pecs etc from the 5x10 benching…I felt like I could have done a lot more each workout. Deload week was almost like “pretending” to work out. (Compared to what I was used to doing) I almost felt like I was getting smaller and softer, but my midsection was getting tighter from all the ab roll-outs etc and that at least was good.
Now, almost two weeks in month two (60%) I already feel fuller and more dense - just more jacked in fact - than I have in a long time 
Needless to say leg days are a lot harder, in particular the 5x10 part…My shoulders are fuller and I am once again sore from the benching. I have also amped up the weight in bb rows, bi’s and tri’s and really like what seems to be happening to me now! Needless to say my legs and back are quite “tender” most of the time…
Side notes worth mentioning are that I almost never benched “normally” before due to shoulder acromion impingement - I stayed with dumbbells and floor press. Now I have no problems with good old barbell benching.
I also do front squats and trap bar deads due to previous back issues and that works just fine for me. I swap between the ab wheel and various crunches for abs every other workout. I have added calf work too because I need it, and change between seated and standing calf work every other workout.
I do bb rows and close grip pulldowns, triceps pulldowns and rope extensions, cable curls and incline hammer curls - changing between days 1 and 3 so I only do one of them each workout. I change between face pulls and prone trap raises as the finisher those two days.
I really can’t say enough good things about this program and I’m really happy I decided to give it a go! It’s everything BUT boring to me and really starts to feel like a challenge. Can hardly wait to find out how the 70% month will make me feel…(scary-exciting anyone?)
So JW - for me you really struck gold with this program!