During installation, I'm asked to install the Microsoft Visual C++ 2005 Redistributable.  That's great, I should already have that.  In fact, I have Visual Studio 2008 installed.

During the install it acknowledges that I have the 2008 redistributable installed, and asks me if I'd like to repair or uninstall that.  I suppose repair is the better option, and select that.  Everything goes fine.  The install completes after that and proceeds normally.

I'm not really sure what I'm getting at here, but it was certainly unexpected.  It's not a bug obviously, and I'm fairly certain it's not conflicting with my previous installation of 2008.  It simply seems curious to have the option to uninstall something at install.  I'm not sure I see a way around this unless you can do some sort of library dependencies check prior to installing the 2005 redistributable.

Food for thought I guess.

On a seperate note, processes running that are using these redistributables will occasionally hang when the installer runs, which will be a significant issue at retail.  It may or may not be related to this:

http://blogs.msdn.com/astebner/archive/2005/12/19/505724.aspx

Some of the replies on that page are especially elucidating.