I was on my last leg of my 4 sets GP 1800 rechargeables when I decided to upgrade.
I had ReCyko in my SB600 and did 4 shoots with it. Each shoot was about 300+ shots with flash. The batteries were still going strong after that. I decided to charge it before my 5th shoot as I felt I was pushing my luck.
I think ReCyko is decent.