If one installs a BootCamp install of Windows, is one thereafter committed to using that install exclusively in Parallels, or can one go back later and access the install under BootCamp? I'm specifically asking because I think that 95% of the time I would like to use an existing BootCamp install as a VM with Coherence, but there may be certain times when I'd want to boot into Windows directly. Is that possible or is importing a BootCamp partition into Parallels a one-way trip?
Parallels just creates Virtual Machine based on this Boot Camp Windows installation. You can use Windows directly under Boot Camp any time you want. And even if you delete Parallels Virtual Machine, Windows under Boot Camp would not be affected.
So are the two installations completely separate or are they somehow synchronized? In other words, if I install a program or make some other change in the BootCamp version, will it show up in the VM and vice-versa?
Native Boot Camp and Boot Camp inside Parallels Desktop use the same physical partition on your Mac to store data. That is, if you install some application in Windows being booted in Parallels Desktop and then reboot into native Boot Camp, the application will be there. Same with files stored on HDD.