I tried some and they're not bad. Personally, I rated them with the Sharks but not as good as Astra SP or my preferred Lord Platinum. Still, not a bad razor blade.
I got a couple of decent shaves out of the one Rainbow I tried. My impression for this too-small sample is that Rainbows may be comparable to other Lord Industry blades (Lords, Racers, Sharks, etc.). There's long been a suspicion that they're all the same blade but with different labels/packages.