My general rule of thumb is to NEVER make a devil deal or take a curse room item if I don't know what it is. I'm certain Dead Cat is always there on purpose.
If you have the Curse of the Blind:
Boss items are safe: only bad one is Experimental Treatment, and possibly health ups if you have half a heart/no red hearts and want to exploit that.
Shop items are safe, but many are Use items so it could waste the 15c. But if you have tons of points, why not. Broken Stopwatch is the closest to a bad item, worth the risk IMO
Devil Deal items are mostly "safe" but not necessarily worth the health. Dead Cat is a possibility and easily the worst to get depending on circumstances
Angel Room items are safe. Can't think of one with negative side effect.
Item rooms are risky at best. All the worst items are in the item room pool. Then again, it's the largest pool, has almost all the best items.
Secret Room items are risky. Cursed Eye is one of the rather small set. Possibility of a 1 Up isn't worth Cursed Eye IMO, but most other items are fairly decent. Missing No is fun but can also screw you over.
Gold Chest items are mostly safe, but you can get Bob's Brain. It's the only one with negative side effects.
Red Chest are risky only due to Dead Cat. I consider it worth it as they're free, and at worst you get Dead Cat and 1/3rd of Guppy.
Boss Rush item is complete insanity. There's no way two unknown items are worth all the wasted time unless you need to do it for an unlock.
Personally I ignore Devil Deals and Item Rooms for the most part, though if I have tons of health, why not, most of the 2 heart items are good. I generally won't use shops but only because I don't want to waste money, they're pretty safe if you have more money than you know what to do this.
But I know what you mean, I'm really happy with the end result we got.
