Emulation is a good idea. HP spent a huge amount of resources to try to ensure their calculators return the best possible numeric results. It is an issue many people forget about, for example, compare the statistical function accuracy of Excel vs R or Gnumeric.

As an example in the calculator world, I like free42 and had it installed on my Palm. However, I don't have the same confidence in it as I have in my HP-48 or my HP-35s. If I'm doing engineering calculations then I really prefer to use a real HP calculator or an emulated one using original firmware.