I think the HP50g is worth getting if you are willing to write your own programs. In my experience, the HP50g is really a handheld computer, and so is most useful if running programs that take advantage of its increased power, memory and screen size. As you may be aware
http://www.hpcalc.org/ is a good source of programs contributed by HP user’s. You will find a number of free electrical engineering programs there as well.
I also like MathCad 14. Actually, I first model my programs in MathCad for verification and debug purposes. However, I write for the HP50g because it is free (when running the emulator) and quick and portable (when running on the physical calculator). It’s also a lot cheaper than the cost of a MathCad license for most users.