(and see comments on the new HP-50g, below)
The HP-49g+ is a new machine, but it implements the HP-48 (give or take) as its front end. It is possible to go behind this and get faster processing, directly from the processor.
The keyboard leaves a bit to be desired, but otherwise it is a useful machine. It uses USB as its wired connection, and can handle an SD (Secure Digital) memory card, although it is for 'archive' uses rather than direct memory access. It has a big screen and a lot of capabilities. However, adoption from the HP-48 is a bit slow in the surveying community.
I bought an HP-49g+ in late 2003, but didn't use it much, as I had many other potentially useful calculators around, as well as computers and the like. Since I had been a big and long-term fan of the HP-48 (and the HP-41 and HP-65 before it), it was taking a while to get to know and love the HP-49g+.
I had bought an SD card for the calculator, but tended to use it with a thumb drive rather more, so got another one just for the calculator. I still have a little difficulty coming to terms with now having a gigabyte of storage in a calculator. It seems just recently that we were stunned at being able to get a megabyte into an HP-48!
When I went to try the SD card, I found that the calculator was totally dead. I replaced all the batteries and pressed the reset button: nothing. Called HP and received two pieces of advice. First was to take a paperclip or similar implement, and see if the flat spring thing that contacts the positive terminal of the top-most AAA battery was sitting up a bit. Second was to take out all the batteries and leave it for 48 hours, and see if that got rid of any static charge. It would also get rid of anything in memory! Fortunately, there was nothing of consequence there.
Having has a bit of a go with the straightened paper clip (to no avail), I left the calculator for over 48 hours. Reinstalled the batteries (just the AAAs first, see if that is OK, then replace the lithium battery, check if still OK). Again nothing.
At this point, it looked like the machine was a junker. But I decided to try the paperclip on the contact again. I also tried to see if I could make contact with the paperclip between battery and spring thing, and was rewarded with a bit of a beep. Getting into the spring thing more seriously, I was able to deform it a bit, so that the calculator would finally start up and run. The SD card came up with almost all of the 1 Gb available, so everything looked great.
Moral of the story: if it looks totally dead, try the positive battery terminal for the topmost AAA battery. This may be all the cure you need.
At some point in the not-too-far-distant future, I will start writing programs for the HP-49g+, as well as the HP-48GX. When I get some decent ones, they will be posted on a parallel website to this one, which is dedicated to the HP-33S.
I think that the HP-49g+ will ultimately be the long-term replacement for the HP-48, so we had better prepare for it. Well yes, that's a silly statement, as it already is the replacement from HP's position, but what I mean is that the HP-49g+ will be what we tend to use in that role. However, there are a lot of other useful machines that can also work as data collectors and calculators, and we need calculators a bit less in the field with laptops so readily available and more stuff done by digital equipment. The role of the HP-49g+ will be significantly different to its predecessors, but will still involve surveyors and their real needs. Let's see what we can do to be ready.
Added Note, May, 2007.
HP have recently introduced the HP-50g calculator. It apparently replaces the HP-49g+, as this machine is no longer offered for sale on the hp.com website. The HP-50g is very similar to the HP-49g+, but it has two significant changes. First, the keyboard is far, far better than the HP-49g+ (and its bretheren) as far as feel and sound is concerned. It feels much more like the HP keys of old: softer, but somehow more positive. It feels almost identical to my HP-48GX, and the difference may simply be the age of the HP-48GX. The keys themselves are, effectively, identical to the HP-49g+, in layout, but it's the feel that has changed. I lot of people apparently complained, and it looks like HP listened and acted! This may be the one we have been waiting for as the real successor to the HP-48 series.
There are now white and orange keys for the extra functions above each key, but this is partly because the case is all black. The writing is no harder to read (being identical in all but color) than the HP-49g+, but there is no background shine from the HP-49g+'s silver case.
The other change has been the addition of some more functions to the calculator. I'm not sure how many of these are relevant to surveying, but they will doubtless make the calculator more attractive to a wider market.
There are some changes to the internal memory configuration, in that the FLASH memory area is a little larger. Also, the HP-50g uses 4 AAA batteries, rather than the 3 AAA batteries in the HP-49g+. Hopefully, this will give a longer battery life.
A final couple of notes on experience thus far. With the availability of 2 Gb SD cards, I tried one in both the HP-49g+ and the HP-50g. Neither were very happy with them, and wouldn't format them or access all the space. However, both are very happy with 1 Gb SD cards. So, it appears that 1 Gb is the limit on SD cards for these calculators, although if you want to key in more than a Gb of material, good luck! If you need more space, get a second 1 Gb SD card!
In Chapter 18 of the HP-50g manual, there is a short section on formatting the SD card. You put the calculator in a special mode (with the System Menu) and formatting the SD card is one option. When I tried this, it didn't seem to format the SD card very well, and I couldn't quite the System Menu. I had to take the main batteries out to get it to stop! So use this mode with caution! The 1Gb SD card was formatted in FAT16 when I bought it, and I reformatted it by putting it in a jump drive or thumb drive and using the USB port of the computer.
I think that I will skip doing much development for the HP-49g+, and go straight to the HP-50g. Of course, anything on the HP-50g will run on the HP-49g+, and even the HP-48GX, if the correct functions are installed on the older machines, but I think we have the new model for the long haul here.