I was just chatting with one of the other developers in my group (Mitch), and he mentioned a bug that just popped up on our radar. In our bug tracking system, there's a field called "NumInstances" which indicates the number of people who have encountered the bug. The OCA system is hooked up to this field, so each time a distinct customer reports a particular problem, the OCA system automatically updates NumInstances (at least that's the way it looks like it works :))
On this particular bug, the NumInstances was high - more than triple digits, all of which came from the RC1 build (which has been out for about a month now).
IMHO, this illustrates the huge difference between bugs in the OS and bugs elsewhere. Bugs in the OS show up and immediately affect millions of customers. A long time ago, I wrote the parable of "One in a million is next Tuesday", that also applies to bugs in Windows - if a bug in Windows affects one in a million users, that means that there are hundreds and hundreds of people who are affected.
Mitch was talking to his brother Mike (who used to work with me on Exchange), and he mentioned this bug. Mitch commented on how many people had seen this problem, and Mike commented that it was sort of like Exchange bugs.
When Mitch relayed their conversation to me, my only comment was "Yeah, the Windows bug is much worse, but in a better way".
You see, the problem has to do with the direction of impact. Both Windows and Exchange bugs are horrible, and cause distress. But Windows bugs tend to affect individuals, while Exchange bugs tend to affect enterprises. A Windows bug typically affects one user at a time, but Exchange bugs affect THOUSANDS of users at a time. Now of course, it depends on what part of Windows and what part of Exchange you're dealing with. A bug in a disk driver for Windows can affect thousands of users, and a bug in the anti-spam filtering system might only affect one mailbox. Similarly, a problem in parts of Windows (like the Active Directory) can take out an Exchange server.
There's a corrolary to this "direction of impact" issue. Because a Windows bug affects individuals and there are many hundreds of millions of users running Windows, each bug has the potential to affect millions of users (and thus have an insanely high NumInstances). But an Exchange bug might only affect one or two enterprises (and thus have a NumInstances of one or two). Each of them has the same aggregate impact, but they express themselves in radically different ways.