I've had an interesting experience with Windows Vista. At first, the OS was shutting down some of the applications, apparently at random. Vista has a memory access protection system (called DEP) and in case of a very unusual memory access a program is terminated, as it is considered as a possible attack to the system integrity. I was quite puzzled at first. Then I started getting abrupt system restarts and/or blue screens. Many of them. I could even boot and the system was gone.
Having had a few troubles with drivers, I though one of them was the culprit. For example, almost on every boot Vista re-installs the audio driver with the default Microsoft one (which doesn't work for my hardware) and it did replace the video driver and one of the motherboard drivers with a different version. So I tried to reinstall and discovered many interesting features. Booting with the setup DVD, you can revert back the system to a known state (although Vista missed some of its own driver re-installations). If you have a system backup, you can restore it directly. However, having a corrupted system file is not contemplated. I wanted to do a system reinstall (as I was getting errors in one core DLL) and had a hard time, as you cannot update/reinstall a system unless you boot it. I could boot only in safe mode, but you cannot reinstall/update from it (you can also do a clean install). Odd.
While doing more experiments I found a very handy memory check procedure. Well, the first time I run it it missed the error, but later executions helped me track the problem. What I find very odd, though, is that the memory test, which is executed at boot time in "DOS mode", gives you only a generic message that everything is OK or there is an error. In fact, it tells you the memory error report will be displayed as you boot the operating system as log into your account. However, with the system crashing on login, I could not get to see the report. I think this is a very naive approach: in case of system errors a low level / DOS or file based complete reporting would do better. Also, when I finally got to see the error report, it says only that there was a memory error, with no extra details.
Overall, even if I got quite upset during the process (my fault was not to fully trust Vista!) I have to say the OS is more robust and has a number of failure protection and restoration mechanism not seen before. On the other hand, they seem to over-trust themselves, as low level error messages after login, no way to update corrupted system libraries, and no way to update the OS until after a correct boot and login can prevent you from using the system in case of a bad crash. Like the one I had.