The HP49g+ is HP's most powerful graphics calculator to date - It is pprobably the most powerful calculator in the world (what can I say, I'm a HP zealot).
It ia improved over the HP49g is almost every single way - the screen is bigger with more contrast, it's faster, has a nice keyobard (but not quite as good as the HP48), and many other features.
Here are some technial specs...
75Mhz ARM CPU
SD card slot (128MB cards work, don't know about any larger ones)
USB and IrDA Ports
Tactile Plastic Keyboard
Performance: 3 to 7 times faster than the 49G
Display: 131 x 80 dot-matrix LCD (much higher contrast then HP49)
Power: Three AAA and a lithium backup cell
Documentation: Quick start guide and 800 page Advanced Users Guide
It is a nice gold colour, and looks more professional then the ugly HP49.
For the cost, you could buy a PDA. But then you wouldn't have built in maths software, nice keyboard or long battery life. It wouldn't be allowed in exams either.