Well, BETA2 of Visual Studio 2010 was announced with GO LIVE license, upgrade capability to RTM and side-by-side working with existing VS2008 installations.
Well, maybe if you are using Visual Studio to compile and run your “Hello World” Console or Web Application you will have no issues running side-by-side.
However, if you really want to explore all the new technologies, while still keeping “old” projects running, you simply can’t use both Visual Studios side-by-side. And here is one particular case in which you simply have to choose whether to stay on VS2008 or go for VS2010 and migrate your projects to 2010, because they will not be supported on VS2008. The special case is called:
RIA Services is designed to make our Silverlight life easier, but instead it brings only troubles (when using side-by-side). And why? Because WCF RIA Services works either with VS 2010 and SL4 OR VS2008 SP1 and SL3. There is no side-by-side! If you have existing project(s) on VS 2008 SP1 with WCF RIA Services, you simply can’t go and explore VS2010 SL4 and WCF RIA Services within VS 2010.
Although you might want to say it is limitation for WCF RIA – yes, it is. But I can use both VS2010 and VS2008SP1 for Windows Azure projects. And for me – side-by-side, means “side-by-side” without any “but”.
So for me so far – no side-by-side.