This is a canny business decision by HTC. The main problem with Android device manufacturers has been lack of continuing software support. Making an unlockable bootloader allows HTC to free itself from an long-term support commitment while simultaneously silencing the very critics that were pushing for that commitment in the first place.
I don't see the problem. The only people who really care about software updates (in the absence of show-stopping bugs) are those that are willing to install custom ROMs. We have a healthy compromise here that keeps both the carriers and the nerds happy.
I think we need to temper our expectations with respect to the mobile device industry. We might see smartphones as mini-computers, but the companies that make them do not, and neither does the vast majority of their target audience.
Anyone installing apps on their phone will probably expect software updates. If their phone they bought a year ago won't work with the latest versions of their favorite Android Market games, due to requiring a newer version of Android, they'll notice.
I don't know that end users would end up noticing.
I certainly haven't (with the exception of trying to use a G1 after a Froyo device). When I got the Froyo to Gingerbread upgrade on my G2 there were many improvements, but nothing I noticed that affected third-party apps. Even many of my favorite apps that use Honeycomb features (e.g. Plume, Kindle, Google Music, Firefox, etc.) seamlessly support older devices.
Google has been pretty good about putting out compatibility libraries for major new APIs (e.g. Fragments) and there's a lot of support for checking the presence or absence of various features / APIs / etc. These days, there's even support in the Android Market for having different versions of the same app for different OS versions.
Supporting a range of OS versions is certainly work, but I'm not sure how much more work it is beyond supporting a wide variety of form factors, different hardware features, etc. In any case, the good developers seem to be able to handle it.
I'm not saying it's a problem. In fact, I think this is the best course of action that HTC could have taken. All I'm pointing out is that the motivation isn't as selfless as it might first appear. This move has a direct benefit for HTC, as well as for HTC's consumers.
