I've developed on Palm, PocketPC, and BREW, dabbled in J2ME, and watched from afar as others suffered under Symbian. Compared to all those OSes, I'd take Palm in a heartbeat for many tasks and it's still the only OS I really want to carry around in my pocket. It is a strange beast, don't get me wrong, but what's happened since the Palm/PalmSource split is that Palm has built a lot of great addons to the OS that are available specifically in the "Palm SDK". This includes a/v codecs, network libraries you didn't get for free in the old PalmOS, an HTML control (thank Jesus), etc. Developing today for a Treo if you know what the device can do for you beats the pants off almost anything else. J2ME never works the same way twice, BREW is nice enough but still doesn't do a lot of basic stuff multimedia devices need to do (ever tried streaming audio?), and Symbian is the biggest pain in the ass in the world to develop for; simulators don't work, devices are super buggy, etc. I will admit that the tools are great for Windows and you get a lot of stuff for free, but the sheer simplicity of the Palm interface really lends itself to smartphone apps, and the Palm tools are, if aging a bit, pretty solid.
As a consumer, you get a large library of preexisting software (it's not all great, but some of it certainly is) and a device that does frickin EVERYTHING. I know people complain about multitasking and how it's not in PalmOS, but the fact that the OS allows only one user thread (and that's by design, BREW does the same thing) doesn't stop there from being a bajillion system threads, like those for playing music, fetching e-mail, handling calendar alerts, and taking phone calls. Plus I have my GPS and my MobiTV and my God knows what else. I own an iPod primarily because I used to do some accessories work, but it pisses me off that I can't integrate with iTunes on the Treo, because I'd buy a big SD card and be done with it. Done correctly, this kind of convergence will kick so much ass that there will be no reason not to buy an Apple-powered Treo, with or without a new OS.
I repeat: as a phone OS, PalmOS really does very well. I love OSX, but why throw the baby out with the bathwater?
