Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Had it for 18 months, then keyboard started to break

Pros: This calculator (and presumably other HP 48/49 calculators) has an operating system that far surpasses TI's in usability. The angled keys are really nice to use, when they work.Cons: Too bad it is hard to use a calculator with a broken keyboard. The bottom row's hinge have almost all broken, so the keys are really loose and wobbly. Apparently, the plastic hinge mechanism is really weak and this is a common problem.