Can Visual Studio 2012 be installed side-by-side w/ Visual Studio 2010?

As Reigo said, yes. Here's the link to the official Microsoft page with the information Reigo provided, and more details: http://msdn.microsoft.com/en-us/library/ms246609%28v=VS.110%29.aspx

The .net 4.5 release is an In-place upgrade.

This means that the binaries for .net 4.0 will be REPLACED by the binaries for .net 4.5.

Microsoft has attempted to mitigate the problems this causes by making a "Target .net 4.0" feature. But this is very different from the targeting previous versions of .net (which have been side by side since .net 2.0).

Because it is a in-place upgrade, "Target .net 4.0" cannot really target it. The best they can do is try to manually remove some "features". They have done this (Scott Hanselman had a blog post covering this).

But don't let this fool you into thinking you are really using .net 4.0. Any bugs fixed by .net 4.5 will be fixed on your development machine and not for your .net 4.0 users.

So if you are developing an application "targeting .net 4.0" and you have .net 4.5 installed then you are at risk. If you accidentally use a fixed bug, it will not break for you while debugging.

When you deploy your app to a machine running only .net 4.0 (ie windows xp) then those bugs are not fixed for your user.

For all intents and purposes, those fixed bugs are now "Hidden Bugs" (for developers that still need to target .net 4.0.

The best part is that it does not matter if you use VS 2010 or VS 2012. Once .net 4.5 is installed the bugs are hidden.

See this post for more details: http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/c05a8c02-de67-47a9-b4ed-fd8b622a7e4a/

I've been burned badly by VS betas, never not had a nasty problem getting them uninstalled. Microsoft makes fine software but the installer seems to always be the very last thing taken care of. Problems I've seen is the uninstall not removing components that then screws up the retail edition and the installer not counting on other installed Microsoft products and destroying their configuration.

This one is far before a beta, do not install it on a machine you need to get your job done. Which pretty much precludes having VS2008 installed. VM is fine of course.

I installed the RC yesterday, and found the following:

It causes VS2010 to freeze when running unit tests (this can be worked around by using 2012, or mstest on the command line to run your unit tests)

It causes VS2010 not to be able to compile C++ projects, failing with a link error. Even after uninstalling VS2012 RC, this problem still persists... so I'd advise strongly against installing it right now

So reading all answers, it comes down to this:

• After installing VS2012, .NET 4.5 will overwrite .NET 4.0.
• You can still use VS2010, but it will compile against .NET 4.5 (since .NET 4.0 is replaced).
• Danger: You can no longer safely deploy your projects on machines that run .NET 4.0.

Yes you can, but its always recommended to install earlier versions first. And if you want to open the Visual Studio 2010 project in VS 11, and then later back again, make sure you don't use Visual Studio 11 new features

It can be installed side-by-side but it's not even beta..! Don't expect it to actually work!

See this problem we're having, and this mentioned by Damian in another comment.

I did it yesterday, and uninstalled it today...

Apparently, something went wrong because some apps that I built before started giving strange errors regarding "unable to load module bla bla bla...", so I uninstalled everything, forced the reinstallation of .NET Framework 4.0 and now all works fine again!

It can definitely cause problems. For example:

In .NET 4.0, whenever one tries to save an enum value in LINQ-2-Entities, jup, you guessed it: ERROR when you have 4.0 GREAT SUCCESS when working on machine with 4.5 installed (yes even though the assembly targets the 4.0 client profile!)

So pay attention when using this good new feature that has no reverse compatibility whatsoever.

It works well on 32-bit machine installing side by side but sometime you can get error but reinstalling or uninstalling previous installation it can be installed. I did it during middle of the project and it do not effect previous work also.

As was stated, officially you can but it can cause problems.

If you want to run Visual Studio 2012, I think the safest way is to use the free WMWare VMplayer and install Windows 8 on it then install Visual Studio 2012 there. You need at least 4 GB of RAM but runs better with 8 GB or more. That's what I do anyway.

My main problem has been that one can no longer run unit tests from VS2010 after installing VS2012 RTM! It just hangs forever. Cannot even stop it.

So for now I would say, MS did it again, side-by-side does not work.

I think this may be due to this being a VS2010 installation without SP1 applied.

The good news is the install makes a system restore point. External hard drive backup is the solution to this till a real version comes out or you are starting a project from scratch.

I've noticed that Web & Loadtesting solutions appear broken after VS2012 install. Have taken copies and upgraded to 2012 and they work fine. It's just VS2010 can no longer initiate a test run.

Yes, you can also easly open a project from 2012 in 2010 without issue. as long as its still using .net 4.0.