I use JBL, I changed to this after using stress coat, for some reason it didn't agree with my fish and lost a few after water changes, since I switched I've had no problems, this is just my experience other people probably have no problems!
Up until a few years ago I used API Ammo-Lock 2 exclusively. When I experienced a mini-cycle I decided to change my conditioner although now that I look back, the mini-cycle was probably due to my (then) overzealous tank cleaning rather than the product.
I now use Seachem Prime with good success. It costs a bit more per ml but it goes a long way.