I think it's the best way to train, you definetly need to warm up before you handle maximum poundages. I'm also a believer that high reps can be beneficial as long as you do them intensly and to failure or beyond (which alot of people simply don't becuase it's too uncomfortable) take squats for example, anyone can fail at 5-6 reps ATF, but If you do 20+ reps your gonna get pretty nausious and your entire body will be taxed to hell.
If you want to do it for the sole purpose of warming up, do not do more than a couple reps, and do a couple "sets" of that then go to a heavier weight example when warming up on bench I do this sometimes:
135x 8 (nice and slow)
185x 1
185x 2
185x 3
stretch...
225x 2
stretch...
235, 245 for 9, 7 reps at failure (1st and 2nd working set)
255 for 4-5 reps to failure (3rd working set)
and I never descend in weight unless its in the SAME set, ie: drop sets. I will sometimes make exeptions but I like to always go up in weight not down.