Joshua Goodman split this session up in three parts:

1. Working better together
2. Faster
3. Fewer bugs

Working Better Together

He began with a little history first.

.NET 1.0 was first released in 2002.
.NET 1.1 worked side by side with .NET 1.0.
.NET 2.0 also works side by side with .NET 1.0 and 1.1.
.NET 3.0 and 3.5 only work with .NET 2.0.
.NET 4.0 again works side by side with all previous versions.

Version 2.0 and 4.0 should be able to run in de same process.

Because sometimes a picture can say more than a thousand words here a picture of what the CLR is.
It is the blue box at the bottom ;-)

I didn’t know about this but the work to get a native app exposed to managed code was rather cumbersome. In .NET 4.0 there is a wrapper tool that does all the hard work for you.

Since the launch there are 16 languages available for the .NET platform. For new languages like IronPython, IronRuby and F# new features become available like Tuples, BigInteger and Tail Recursion. All other languages benefit from this too.

Faster

.NET 3.5 SP1 is faster to install and has a faster startup.
New features to make it easier to write parallel/multi-threaded applications Parallel.For , Parallel.ForEach, AsParallel() in LINQ
Garbage collection enhancements: for Server side with notification when Gen2 collection, for workstation with background collection
Profiling improvements: ability to attach and detach performance and memory profilers

Fewer bugs

Corrupting state exceptions: cannot be caught by normal catch statements
Support for dump debugging
Code Contracts: goes further where Asserts stop