Stripped cross-point screw in the case back of a watch.
Badly. The 1.5mm screw extractor from the Precision Screw Extractor Set broke on the first use, leaving me with a big, painful, bleeding hole in my left hand. I am a professional watchmaker, so I can't say that I'm totally surprised by this; manufacturers of this type of tool don't seem to appreciate the torque and stresses placed on their tools for this purpose. Do they supply replacement bits for the inevitable broken ones?
The rest of the tools were AOK, especially the screw extracting pliers which are a god-send.
I don't know if iFixit already does this, but it would be helpful if replacement parts would be available for tools that are likely to break. Generally, though, iFixit tools are great and this single disappointing experience wouldn't stop me from ordering again. After all, iFixit didn't actually manufacture the tool that broke.