My first Windows Mobile device was the i-Mate sp3i. After using this phone for a month I knew I could never go back to having a "dumb" phone. Next I upgraded from the sp3i to the sp5. While the phones look very similar, the sp5 was a big upgrade, especially when the feature pack upgrade came out and it supported push email.
Then a couple of months back, while using my sp5 as my Internet connection, the phone died. At the time I was working on a Windows Mobile project and really needed to have a phone so I walked down the street to the mall and purchased a Treo 700w from the Palm store. After having the 700w for about two weeks I figured out that the reason my sp5 died was because the battery died. So I put my sp3i battery in my sp5 and that phone was back in business. So now I had two phones with two carriers and I needed to get rid of one.
The things that are important to me on a windows mobile phone are (1) portability, (2) internet access, (3) a2dp, (4) phone service, and (5) upgradability. The sp5 is definately more portable, not just in size, but also in weight. The 700w is very large when you stick it in your pocket. The 700w did have better internet access, but I was surprised at how little of a difference this actually made for me. I thought the EV-DO network speeds were going to make it impossible for me to ever go back to EDGE. However, there really wasn't that much of a difference. I also thought that Verizon's "most reliable network" would clearly outshine my T-mobile service, but that was not the case. In fact I actually prefer T-mobile because I got better coverage, better quality, and their voicemail doesn't require a pin and doesn't needlessly repeat things (verizon: you have x unhead messages, first unhead message, the following message has not been heard (okay I get the point already)). The 700w does not support A2DP so I couldn't listen to .Net rocks or my music using my HT820 headsets (technically the sp5 doesn't support A2DP either, but you can make it work).
Finally, one of the most important aspects of a mobile phone for me is upgradability. By this I don't mean I can add stuff to my phone. I mean that I can upgrade my phone whenever I want and I don't have to wait 2 years to qualify. So T-mobile wins again since I can have multiple phones if I want and switch between them. But really this post is about my next phone.
Orginally I was thinking that I was going to get the HTC MTeoR. The MTeoR is the logical upgrade path for me (sp3i (32/64), sp5 (64/64), MTeoR (128/64)). However, there are a couple of potential deal breakers for me. (1) The microSD card slot. The sp5 (and sp3i) took a MiniSD so that is what I already have. If I move to the MTeoR then I have to buy a new card. (2) The connection is not mini-USB. Well it might be. I'm not 100% certain that it is, but right now all of my devices charge via a miniUSB cable (that was another reason the Treo didn't fit in). (3) The name. Do I really want to have to type MTeoR all the time? :)
The device that might steal me away from the MTeoR is the ASUS P525. It meets all my requirements plus it has a stylus which might come in very handy. However, I would like to see how well it works using one hand since the SmartPhone software is made for this while the Pocket PC software is geared more to having a keypad.
I'm not planning on upgrading for a couple of months (since that is when we get our next gadget fund at Avanade) so I still have some time to look into what device I really want. It will be interesting to see where I stand a couple of months from now. :)