Short answer: yes, it's good lead. But you DO need a lot to make a ball.
I weighed the strips once - something like 0.5 grains. I figured it took several hundred to make one 0.535 RB.
Long answer:
I used to collect it from my old dentist. Problem was they just put the bitewings in trash bags with their latex gloves and used paper towels. I'd spend 2-3 hours pulling out the lead sheets from a disgusting mix of all that used crap (covered with dried saliva and chewing gum from the dental assistants).
Not only was it way too much work, but I worried about 'catching something' from the crap.
So I stopped getting it. I never asked if they'd be willing to pull out the lead sheets for me, but I've since switched to another dentist and have a supply of 50 or 60 pounds of lead and do far less shooting than I did even just 3 or 4 years ago so don't go through it as fast as back then.
AND, perhaps more importantly, I recapture all my lead (well, when I hit my ball stopper) from the range. I usually recover about 80% of what I shoot, and it only takes a few minutes to plow through my cardboard box stuffed with magazines. The returns are diminishing, of course, but it's actually considerably more efficient than pulling lead sheets out of bitewings.