Instruct: Classify the given Amazon review as either positive or negative.
Query: Some keystrokes don't register after a year

I bought this for the June 2009 CFA level 1 exam. I had an engineering HP calc during school and decided to go with an HP for the CFA exam. A year up to the exam, it was working fine until just about 2 weeks prior to the exam date. Some keystrokes had trouble registering, requiring multiple key taps. Not good! I had to be extra careful with my entries during the exam which slowed me down a bit but I ended up passing. However, I will switch to the TI for level 2 and keep this one as a backup. Contrary to my past experience with HP calcs, the durability of this model is disappointing, especially for the price. It's definitely a mechanical problem, as I ran the on-board self-diagnostics and it passed. Caveat Emptor!