Doing it right means putting it left
The first thing that hit me when firing up Visual Studio 2005 for the first time was that the solution explorer was docked on the right side of the screen. Funny thing is, it seems the same thing happened to Frans! His motivation of why the solution explorer should be docked on the left side of the screen is correct ofcourse, but while reading the comments one by Bruce Johnson made me laugh out loud, so I'll just paste it here:
If you plan on keeping your Solution Explorer open, your suggestions make sense. On the other hand, I always keep mine collapsed, so I want it on the right side. Otherwise, when it expands, it covers the code that, as you wisely noted, sits mostly on the left.
I'm guessing the decision as to the 'default' positioning was one made by committee. "If we collapse it by default, people won't know where it went to. But if we put it on the left, it makes the code jump around. Why don't we just put it on the right". Hence getting the worst of both worlds. ;)
I remember noticing the default right-side docking when I first installed VS.NET 2003 so it's not a new decision. I remember seeing it on the left by default as well though. It appears to have something to do with the language selection you make when you first start it up: if you select VC++, you'll get the old left-side look from VC++6 (and before), but any .NET-language including C# will give you the VB6-type right docking position. Just goes to show that Microsoft is more concerned with keeping all those migrating VB-users happy than a bunch of those (always-whining anyway) C++ types :)