Of the three hypervisors tested for the Mac, Parallels was strongest in features and usability, and its 64-bit guest virtual machine support provides flexibility for developers. We could run Mac OS X Leopard client or server as a guest.
We were able to import VMware or Virtual Box files (guest VM snapshots, or rapidly mountable VM guest operating systems) easily and it should be possible to import older Parallels files, but we didn't test this.
There were a few minor hiccups after converting a Windows VMDK VM disk-based VM file to Parallels format. We initially had a little trouble setting up, but all we had to do was to remove the VMware tools and install the Parallels tools inside the VMDK file, then reboot.
Parallels Transporter let us convert other formats of VMs into the Parallels format (the .vhd disk file format used by VirtualBox and Hyper-V, and .vmx VMWare disk format).
We tried converting a few of our other VMs; a couple from Hyper-V and one from Fusion and Virtual Box. All worked except one SLES Linux Hyper-V VM. The Win2008 Hyper-V VM we converted worked just fine.
We found this to be a handy feature for developers and software testers although installing the feature took time. The auto-upgrade feature VM-file format reformation process can take a very long time. The problem we found is that it automatically upgrades, and if the conversion process hangs, there's no indication of this. We'd have preferred a manual install option instead.
Windows XP installed easily for us, with no interaction except for entering the username and product key. Parallels has preformatted settings for XP.
Another useful Parallels feature was the ability to mount a Windows VM guest's NTFS file system into the Apple MacOS 10.5 Finder application. We could access all the files directly like an external hard disk. We could easily drag and drop files and folders between Mac and XP VMs. It's even possible to have the Apple Spotlight application index the VM Windows guest drive, a feature that wasn't available in the other hypervisor products.
The Disk Sharing feature, which works with both Linux and Windows VMs, was also useful. Under Linux, disk sharing mounted the directories under the /media/psf directory (Parallels Shared Folders) and in Windows, it created a Parallels Shared Folders shortcut on the desktop for easy access.
When we inserted a USB flash drive, Parallels asked if we would like to mount it in the VM or Mac, if Smart Mount is enabled. VMware Fusion will automatically do it without asking, depending on whether Fusion was the active application or not. Parallels handled USB flash drive use more easily than VMware Fusion or VirtualBox for Mac.
Application sharing worked well too, but this feature is only available with Windows-based guests. We saw a list of applications with which to open files when we chose Open With from the right-click menu. Apple Finder and Windows Explorer listed both Mac and Windows applications to choose from.
We were also able to open Mac files in Windows applications, although sometimes it was difficult to distinguish which were Windows applications in the Open With menu. In our limited testing, we had no difficulties with application sharing, which allowed seamless application use within Windows or MacOS contexts.
In Coherence mode, which is similar to VMware's Fusion's unity mode, the Windows taskbar stayed fixed to the bottom of the screen, hiding the desktop background and playing well with Apple Spaces. But unlike VMware Fusion, the Parallels-based Windows start menu was not hidden by default, and there is an option to change this in the Applications menu. Similar to Fusion, you could see Windows applications on the dock when in Coherence mode (it's also possible to do so in normal mode). This mode does not work with Linux guests.
There was also a new mode called Modality, which puts the VM in a small window so you can monitor it quickly. This feature seems to be most useful if one has more than four or five VMs running. But with one VM, we could get a real-time visual of screen changes, such as compile completions, and so on. It was an easy way to watch the VM. Although the window starts out very small, we could actually resize it.
Disk management for guests is augmented by another cool feature called Undo Disks, where we could delete anything or make any changes we wanted to Windows. When we restarted/shut down or otherwise stopped the VM, we were asked to discard any changes made during that session.
We judged this to be useful in testing applications or allowing safe removal of added applications (such as XP's \Restore application). This capability to roll back to the originally loaded Windows guest VM is handy.
Undo Disks allows the reset of the entire VM, if started with Undo Disk. The same thing could be done with snapshots by reverting to an older version. However, Undo Disk has a limit of one rollback.
Parallels also has a feature that let us create VM templates. Once we were finished installing and setting up a guest OS, we could convert or clone that VM into a template for subsequent reuse. This worked as expected when we tried this with an Ubuntu VM and Windows VM. We were able to recreate the VM exactly like we had earlier. This comes closest to the production-quality rollout of a Mac-based environment's use of virtualized XP (or other hosted operating systems) sessions.