Since there will always be a better version next month, you need to want a month, then another and then another... I've yet to see an upgradable PDA. I have added a memory card or a wifi card, but such is not a full upgrade.
The better track (research?) would be to find the software you want to run and note what PDA runs it.
In my world, I'm considering the Axim X30 w/wifi. That way the data and apps would be on the network so as I upgrade the network I get a better PDA.
Can anyone recommend a PDA that would be useful in the critical care setting. I am looking to buy one for the first time. I need one that has a good memory for reference material relating to drugs, calculations, ACLS, etc. I want an easy to read display and a battery that lasts. I want one that I can easily download programs from the net and from other PDA's. The other nurses I work with all have Sony's. These seem very nice but I am not willing to just go out and buy one without first checking out other options.
On the fun side, I would like one with an MP3 player.
Price is a consideration, but not a big one. I don't want to pay for top of the line and then find out a month later that a better version is out for less than I paid. Are they upgradeable?