I've had a 50g for about a week now. The keys work fine, unlike the 49+. Screen resolution is good, paint is good. While HP purists will whine about the lack of the large Enter key, it looks a lot better than the blue rubber duck 49.
The connectivity software works well with the USB cable, nice and fast. All old 49 programs, libraries, were downloaded, installed, and run without a hitch.
Formatting an SD card is easy, and using it is just another extension of the Filer. A $20 Kodak 256 MB SD card gives immense storage space, and beats the heck out of a $300 1 MB card for the old 48gx.
So far the only bug I've found is one that was reported in comp.sys.hp48: LinSolve doesn't work for any combination of linear equations, so a ROM update is needed there. The workaround for that is to simply use Solve on a vectored list of equations, which will solve any system, linear or non-linear.
In a nutshell, I'm pleased with mine, and will buy more when my budget lets me.
Edited: 8 Aug 2006, 10:15 p.m.