Recently I upgraded to a Tungsten|C (AKA the TC). Prior to this I was using the IIIc. I carried the IIIc for about 2 years and got a lot of use out of it. However with more and more things I wanted to load on it, I found that with no memory expansion I was frequently having to clean off books I'd loaded and archive them on my hard disk & photos looked funny going from JPG to effectively a color-safe GIF format (with the color depth conversion).
After using the IIIc for a little over 2 years I have become frustrated with the Graffiti interface numerous times. It was OK in the beginning - but after a while I began to resort to the onboard digital keyboard rather than write and erase a character numerous times - and over time this got harder and I had to re-calibrate the screen more often. I'd seen the Blackberry units back in 2000, just a few months before getting the IIIc, wondering if they would soon have PDAs that would work like this. Since no one other than pager/email-on-the-go companies were building in the keypads, I went ahead with getting the IIIc, since, gosh darn it, I wanted color.
Well, 2 years later it seems like everyone is either making add on keypads or building them in at the factory. I also enjoy WiFi in my home and the TC had both the keypad and the WiFi built in. Since getting it I've found it to be very convenient. I don't have to go upstairs to my computer room plug it in the cradle to hotsync - I can be downstairs watching TV and just hotsync from there (ditto for a quick e-mail check - my e-mail client of choice for the last 8 years, Eudora, has a client for PalmOS). Migrating to the TC was pretty painless - just hotsync the IIIc and then hotsync the TC and load back all the PDB & PRC files in the backup/archive folder that I want to run. Most of the apps either ran (or crashed but those didn't matter: ex. Fireviewer 5.2.2 crashed - but Palm has a photo viewer out-of-the-box, so I didn't need it anymore, the OliveTree Bible software I was using was really old - a quick trip to their site and was able to get an all new version of the software I had been using - but updated for OS 5)
One thing I've run into is that large files such as MP3 don't play nice when running installation over WiFi on the TC - I usually end up doing those over the sync cable connection, it probably is because the source computer is also running on WiFI and the bandwidth is saturated. As far as WiFI range goes for the TC, I'd say it's as good as my laptop. I've been able to detect several of my neighbors' WiFi access points from the street! (some of whom haven't secured their access points, and no, I haven't been surfing on their nickel despite the suggestion from TechTV's segment on WiFi - this was a purely academic experiment) People that have been having issues with the TC may also have poor ranges on their WiFi access points as this can be just as big a factor as the TC itself.
MP3s you ask? The player that Palm links to for realOne does work with the TC - just the plugin for your PC won't - you'll have to use the Palm desktop software to copy the MP3s over to the SD card (I think this is easier than having to use the 3rd party software to load tracks). I think the reason they list the compatibility for the ARM processors is because they have the liveTrack thing working on that line of systems (the Tungsten|T and Zire 71 are specifically listed as compatible). The other catch is that it will be mono since the audio feature for this unit is that you can record and play back (it uses the same kind of 3-stripe 2.5mm jack my Nokia 3360 uses - not the "usual" 2 stripe jack that you will typically find as a "universal" plug). I think Palm could have invested just a teensy bit more effort and added a second jack with a 3.5mm standard stereo jack.
One thing that periodically annoyed me was the LCD display of the IIIc If I was outside in the bright sunshine I had to cover it with something so I could see what was on the screen. The TC has a much better screen, while I may not see full color, I see something that to me looks like the classic greyscale display of older units, which is perfectly usable if I want to read the meeting alert that just went off in my pocket.
I think in the long run I think I will probably get far longer use out of it than I got with my IIIc because of all the built-in toys. I think that those of you out there that just need a digital address book and eBook reader will be fine keeping your predecessor units, it just depends on what you want it to do. The only real downside I've run into is the battery life with more than a few minutes here and there in a day the battery will drain pretty quick (to the extreme that you will have to restore from a desktop sync).