Like many others here, I think this is a very good and useful thread. I particularly liked the way the OP kept some of the more subjective elements in the forefront while discussing how to choose a phone (or for that matter any kind of device).
What I want to do here is to post about (1) how I came to choose my phone (2) how I use it now, and (3) what my experience has taught me about the next phone I am going to choose.
I find many parallels between what the OP has posted and my own experience. Long post though! So, you are forewarned.
How I chose my phone?
I came to Android from a Nokia/ Symbian combine. I loved my Nokia E series phone, especially the physical KB. But the phone was getting a bit awkward because it was locking up repeatedly for some reason or the other.
I had been reading about Android and so I took the opportunity to buy a low-end Android unit - Samsung G5560 (Fit) to try it out. I now wish I would have bought the Ace, but whatever. When I bought it, Froyo was on as the OS. My reasons for buying the phone were (1) I did not want to spend too much money on what I considered to be an experiment since I had never used Android (I have previously used Palm and WinMob 6.5) and (2) I wanted a phone for only a year before I upgraded. This was to be stop-gap arrangement for the time being. (3) It was well within my budget.
Originally when I bought the phone (around June 2011), I did not have a 3G connection. Though I did have GPRS. But having got the phone, I signed up for the 3G services and have not looked back since.
My impressions of the phone were and remains positive. I found it to be light, easy to handle and sleek. Android was a revelation. To begin with since my stuff revolves around Gmail, setting up was hassle free. Though the extent of my intimacy with Google was and remains a bit worrying.
The phone did hang sometimes, but I attributed that to the low-end specs. Recently, however, Gingerbread was pushed out to the phone and it has worked very well since. Battery life has improved, among other things.
How I use my phone?
Obviously for calls and messages. But I have found that my earlier interest in surfing the web on the phone has died. The screen on my particular phone is too small. I also use my phone as a music player (I use the doubleTwist app from the Market).
Having once tasted Android, I looked around for a tablet and since Android tabs and the iPad were the only choice, I went with an Android Tab (Acer A500). I have never used Apple stuff. And, anyways, they are too expensive for me, though I do appreciate the designs of their hardware.
I use my tab for everything except for making and receiving calls. To do that, I tether the phone to the tab using the MobileAP feature and it works brilliantly (though, at the cost of battery life). This is one feature that I really like and use a lot. Any future phone MUST have this feature and it should be dead-easy to set up.
So, essentially, my "smart phone" (low-end though it may be) is basically a phone, media player and access point to tether my laptop (Win7) and the tablet. In a pinch I can activate the other features, but I keep it off to conserve battery.
What about my next phone?
If the above is what I am going to use a phone for, then what I need - and this specific only to me - are the following:
Good battery life (quite essential)
Wif + BT capable (non-negotiable)
Sync-ability with tab and laptop via Google/ Gmail (or it could be MS Live Services too)
Seamless tethering (non-negotiable)
Efficient messaging system (I am willing to try out any new but reasonable solutions)
Something that complements and augments the tab (quite essential)
Now, the question remains: Will the next phone-tab combo be an Android affair or a Win8 affair?
Nokia hardware (phone + (possibly) tab) + Win integration (hopefully with tab-centric Office apps) sounds good since I also use Office extensively. Very tempting! Would involve migrating to the MS eco-system, but that's not too much of a hassle. Also, though I am assuming the update schemes would be more stable than Android, the Nokia-MS combine may get a bit claustrophobic (and expensive).
OTOH, I still feel that Android is and will remain more exciting - both in terms of OS and apps and hardware though Nokia's quality will remain hard to beat. Potentially, more VFM to be found on the Android road.
In the Android scheme of things, one thing that I will do when I buy my next phone (end of 2012) is that I am going to root the Samsung Galaxy Fit (before it is too late - it may already be too late) in a way that optimizes it as a media player with consequent battery advantages. I may want to use it as a dedicated media player thus freeing up a function for my next phone. Trade-off? I am adding another device when the objective is to be mobile and to benefit from the convergence of not only information but also hardware.
The main point is that I can do any of the above in either eco-system. So, I need to only look for the appropriate hardware that can support these activities.
This is probably how I am going to go about choosing my next phone.
Again, sorry for the long post!