I've had both installed on several system with no problems. I currently do development on both 2010 and 2012 projects on the same system with no issues (I also have 2005 and 2008 installed just in case I have to work on any legacy programs).
That said, there are some potential issues.
As noted in the thread you linked, which mostly covered beta and RC issues, there can be issues with certain differences between the 4.0 and 4.5 versions of the Framework. You may want to review info on these differences to make sure they don't apply to you. I haven't encountered any of these myself in WebForms, WCF and MVC projects but every project is different.
I'd also recommend compiling all projects (libraries, test projects, etc) referenced by your primary project to the same Framework level. I've done this with my projects to prevent any problems. I just created a branch for each Framework.
Speaking of branches, TFS works differently in VS2012 and VS2010. This one bit me and I had to run TFS manually in 2010 for my 2012 projects until the TFS team got things fixed up correctly on their server.