I think there are three important ingredients for a great phone and if you can get all three together then bingo...at the moment I don't see anything out there that does all three superbly.
Part one is like property except it is not all about "location location location" but rather it is "apps apps apps". Myself, there are typically only a few apps that I will use on a regular basis on any device and these are email, browsing, RSS feeds, ListPro, a password application (eWallet), diary for meeting syncing, a weather forecaster, basic Office files and a bit of ebook reading. That's about it. Platform wise at the moment, I can get all these things and in particular, specific programmes like ListPro and eWallet for both palm and windows mobile. The rest I can cobble together from onboard apps and existing cellar-ware stuff I have lying around. At the moment with the iPhone things are not quite as good on this front although jailbreaking has added in a couple of things I was desperately missing and obviously the sdk thing should make a huge difference and raise it to the level of the other two platforms.
On that front then things are almost equal, palm and win mob are out in front with the iPhone all set to make a late charge on the outside. If apps however were the sole consideration I think I would have Palm as number one.
Second important consideration is not platform because I believe you should choose your platform after assessing which one meets all three of the criteria best. So, number 2 important consideration is hardware and specs. Some of those important apps you use will work better if you have certain specs on a device. For example, RSS and browsing are better on wifi or 3g equipped devices and whilst obviously if you are a big sat-nav person then you would prefer a device with GPS built in for convenience. There can be little doubt that windows mobile is King here, the range and breadth of devices available wipes the floor with both palm and the iPhone...at the moment. The iPhone is getting there but we need to wait and see what features/hardware is added via version 2.0 to see whether it can compete with windows mobile and the same applies to any future palm smartphones running Nova. Believe me, running an iPhone without wifi and having to browse via GPRS is a painful experience that detracts considerably from the benefit of having a top class browser on board so in that sense, hardware and specs are important.
Likewise, I'm sure TyTn11 owners would say the same about watching videos on their devices....if there is something you will be using a device a lot for, make sure it can do that thing well.
Last but not least is useability. You may have all the apps you need and the hardware specs look great but if the device is a pig to use you will soon tire of it as frustration sets in. I feel this, for me, is where windows mobile falls down and where palm and the iPhone really step up to the plate in style. What they have in common is that out of the box they are both relatively "settings free" and thus set up for almost maximum ease of use. Contrast that with win mob which necessitates an almost anal "settings" tweaking/tinkering obsession which is perfectly acceptable to some (and good luck to them) but which now completely passes me by on the interest front. I just cannot be doing with it anymore.
I daresay if I could be half-bottomed to make a fist of it, I could end up with an almost perfect windows mobile device but then when that was achieved there would be the memory management issues and slowing down of the system and that would be the something else that would start to grate on a near daily basis. I've had too many win mobbers over the past two years that have started off well and then fallen by the wayside as they turn from well behaved power people into sulky and temperamental teenagers. I thought for a while last year that the HTC P430 I had was going to be the answer...nice form factor, good keyboard, lightish, wifi, great battery life. solid as a rock but then I went and ruined it all when I upgraded to Win Mob 6 and was left with about 12mb of free RAM to run apps in.....major league memory issues resulted which made it almost unuseable. Drat....another device like that with similar specs but lots more memory and quicker nav would be attractive. I am also tempted to buy one off ebay as long as it had win mob 5 on it.
So, for the moment the seach goes on but I have a feeling it will end when either the iPhone 3g and apps come out or if not, when devices sporting the new Palm o/s finally appear.