2-3 years ago I've been an huge HTC fan buying every 6 months a new HTC handset until I realized that they want you to buy new handsets all the time with their business model, Sense and reluctant update policy. The rest of the crowd (Sony, Motorola, etc.) isn't better but the case HTC feels shady—these guys shotgun tons of new phones per quarter to the market with many many variations of Sense, their drivers, witholding sources, etc. to make it impossible to update their crappy phones.
As a data point, I can add that I bought an HTC HD2 back in December 2009. It had come out a couple of months before, and the hardware was very nice - it stayed at the top until this year. However the software was Win Mobile 6.5; it was occasionally updated, but the updates page went away (in a 404 way) back in October 2011 or so.
So, about two years, and gone. Not quite fly-by-night, but not too satisfactory.
(Workaround: using the original OS as bootloader to an Android from XDA-developers ...)
