To really make your case, you've got to understand a few things about the
various .NET Framework versions.
Historically, Microsoft has introduced a new Visual Studio product to
accompany a new Framework version, they did that with Framework versions
1.0 - 2.0 as follows:
Framework v 1.0 --- VS .NET 2002
Framework v 1.1 --- VS .NET 2003
Framework v 2.0 --- VS .NET 2005
Obviously, the 2.0 Framework represented major modifications to the core
software (new compilers a new CLR, etc) and so, of course there were bugs.
There have since been service packs for both the 2.0 Framework and VS 2005
to address these issues.
Then, Microsoft did something a little different, they introduced some new
..NET technologies, but instead of creating a *whole* new Framework with new
compilers, a new CLR, etc., they made a new Framework version that just had
what was necessary to run the new features (Windows Communication
Foundation, Windows Workflow, Windows Presentation Foundation) and called
that Framework version 3.0. Instead of making a new version of Visual
Studio to do along with that, Microsoft created a plethora of add-in's to VS
2005 that would make it work with the new 3.0 stuff.
Now, the latest version of the Framework is 3.5 (adds additional support for
LINQ and Ajax on top of WF, WPF, and WCF). For this new release (now that
most of the bugs have been worked out, Microsoft has released Visual Studio
2008, which works against the 3.5 Framework (there are no add-in's and
service packs for this - - yet).
Essentially, VS 2008 gives you access to all of the new Framework stuff AND
is really VS 2005 with all the bugs worked out. It is considered a very
stable product and has the advantage of making all the latest .NET
technologies rolled up into it.
I know you said that you were not interested in the new stuff, but for
essentially the same price, why wouldn't you want the product that is more
stable, has less updates and patches to keep up with and gives you more
features. That's the argument to make to you boss.
Goo luck.