.NET Framework 2.0 vs 3.5/4.0... any possible advantage to use the older version?

My project leader insists on using Visual Studio 2005 which only targets the .NET 2.0 framework and only supports C# 2.0 syntax.

He insists that the 2.0 framework has higher compatiblity and performance for older computers. By old, I mean 5-8 year old Windows XP machines.

Assuming we only support a minimum of Windows XP / Server 2003, is there any advantage at all to using .NET 2.0?

I am pretty sure that even targeting .NET 2.0 we can take advantage of C# 3.0 syntax in our code (lambdas, auto-implemented properties, etc.) if we upgrade past VS2005.

.Net 2.0 is considered to be more widely deployed, but 3.5 isn't far behind any more. However, that's no reason to limit yourself to Visual Studio 2005 or C# 2.0. Visual Studio 2010 can target .Net 2.0, and use C# 3.0 features when it does so to boot.

.NET 2 is no longer supported by Microsoft. Well, Microsoft makes the terms tougher to explain. For Windows XP and Windows Server 2003, you have to at least use .NET Framework 3.5 SP1,

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so that you can receive assistance from Microsoft support team.

Therefore, I see no reason to stay on .NET 2.

"the 2.0 framework has higher compatiblity and performance for older computers" is a joke for me. When you lose support-ability from Microsoft, you lose everything.

Normally, people who would like to use the older version is mainly because they think the old one is more stable and better to production.

But .NET 2.0 is quite out of date already, and .NET 3.5 and .NET 4.0 have been proven to be very stable and make things easier. (such as LINQ, you can try functional style programming via it, very fluent and productive)

For the IDE part, Microsoft rebuild the visual studio 2010, it is more stable and productive, and it is also can target .NET2.0 if you want.

So, why not use Visual Studio 2010 instead of 2005, even if your project is purely .NET2.0, the former also has downward compatibility.