I have used it on about 20 L3+ so far. That might go up based on reliability of the modded units.
The big benefit for me is not the $ saving on electricity or any boost in hashrate.
It reduces my overall temps and pulls my electrical current consumption back to safer levels.
I was planning to monitor my machines for a while more before donating, but it's worth .25 LTC and more to me, so here's my first transfer.
There will be more if I'm still happy in a month or so.