You've never heard...
"If it isn't broke, don't fix it..."
or
"Leave well enough alone..."
or similar phrases?
In other words - why would you "update" to something if you have no
need for it?
If nothing you has requires it - don't bother.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnlong/html/netfx30.asp
Says:
"... How .NET Framework 3.0 Relates to .NET Framework 2.0 and
Earlier
The .NET Framework 3.0 adds new technologies to the .NET Framework
2.0, which makes the .NET Framework 3.0 a superset of the .NET
Framework 2.0. You can think of .NET Framework 3.0 as an "additive"
release to the .NET Framework 2.0, as contrasted with a
generational release where software is revised across the board.
(For example, the .NET Framework 2.0 was a generational release
over the .NET Framework 1.0.)
Because .NET Framework 3.0 is an additive release and uses the core
run-time components from .NET Framework 2.0, it is completely
backward compatible with the earlier version. Your existing .NET
Framework 2.0 based-applications will continue to run without any
modifications and you can safely continue your investments using
the technologies that shipped with .NET Framework 2.0.
If you are moving to .NET Framework 3.0 from .NET Framework 1.1 or
1.0, you should perform impact analysis and run compatibility
testing prior to deployment. While we have worked to make .NET
Framework releases compatible, there are a small number of known
incompatibles due to security and significant functionality
additions. For more information, see the page Breaking Changes in
.NET Framework 2.0 on the Microsoft .NET Developer Center Web site
..."