Big aid in lifting from a couple of perspectives:
1) When somebody says you're looking good - look back at what excercises and schemes work for you
2) Ability to switch excercises around - run the gamut on all your recent back excercises - look back 1 year ago and I'll bet there's one or two you have forgotten about
3) Gauges.
I note if I took: Caffeine, Ephedrine, Yohimbe, Tyrosine (or any combo of them)
Also note: date, start time, end time, warmup and length, weights, reps, sets, time between sets, use wrist straps or not, mixed grip (esp. on deadlifts)
Sounds like alot of work - but once the habit starts - an extra 10 seconds after a set is no big deal. And the benefits of having all the info to look back on is invaluable.