i've been an avid user of palm pilots since 1999, and the most recent one i have is the Palm Tx (same as tungsten Tx)
I also believe it is a dead end.
The current number of apps available for it are good and useful, but no new Palm devices will ever be made (since Palm is coming out with a brand new OS)
so there is no reason for developers to make new programs or update old ones.
also, even though the Palm Tx has Wifi and bluetooth, the web browser and email client is very bad. websites, especially those with java or flash (anything beyond simple text and pictures) don't look right.
iPhone/ipod touch - I've owned an ipod touch before I switched to the iphone. The sky is the limit in terms of applications. With the fact that anyone can write an applicaation and become rich, it's no surprise that there are now TONS of apps for the iphone/ipod touch that are medicine related. You can even view MRIs on the iphone (of course, your hospital must be using their corresponding MRI viewing software)
the only thing that the Palm Tx/Treo has over the iphone/ipod touch is UptoDate. You can use update from your iphone and ipod touch, but you must be connected to the internet. You do not store their articles on your iphone/ipod touch. With the Palm Tx/Treo, if you have the cds, you can install the articles on a memory card that you put in your Palm so you can access it whenever, whereever.