You won't be able to access some Windows directories (because Windows redirects 32-bit apps to different directories), so you won't see or be able to execute some x64 apps.
On the topic of this redirection, when using the x64 version, is there any way to detect that this folder would have been redirected for a x86 app and display the x86 folder?
I run into the annoying situation where a x86 app refers me to a log or configuration setting or something that it sees in one directory, but I have to guess at what directory really contains the files. I'd love to invent a "cdx86" alias that would change me into the directory that a x86 app would see.