We have now the opportunity of offering free shipping for the HP Prime. This is a chance of getting the best calculator made today! The changes in the firmware have made a better, more stable machine; all the birth pains are over from one year ago; and its open hardware implementation allow for future improvements. We know that they are working on three-dimensional graphics, but there may be other very interesting things.
Its architecture makes it very easy to customize - just look at my business customization threads somewhere else in our website. And its rechargeable battery makes it much more convenient - you can recharge it at any place with any of your micro USB chargers - even off your computer.
There are some missing items that I hope will be solved with its update-ability, like using it as a USB keyboard with your laptop: the convenience of a numeric keyboard with the lightness and keyboard feel of your trusty HP calculator.
From the speed point of view, it runs circles around any other calculator, exception made of the HP30b/20b family, based on similar technology. (While both the new HP12c Anniversary and the new HP15c Limited edition were based on the same technology, they were using the original firmware on a software emulation of the original hardware - this 2-layer set up made it less performant than the above calculators.
You can find dedicated software (including games, which are surprisingly fast for a non-dedicated device) here: Software for HP Prime, and there are a number of dedicated pages with more and more software for it.
While it is the most powerful calculator ever designed by HP, it has been designed with the student in mind. This means that, unlike other calculators, it has a rugged protection case that can be adjusted in the back for desktop use, a beautiful but resistant metal front and a hard plastic back, and a battery bay with screws (no more lost battery bay covers lost)