First, Parallels promises that you'll get a real Start menu, not the silly button in Windows 8.1 that merely switches between the Start screen and the Desktop —which the Windows key on your PC (or Command on your Mac) already does for you. But Parallels' Start menu is not there out of the box. To get it, you need to ... well, I don't know. I couldn't figure it out, and Parallels didn't respond to my several queries. You might as well get an app like Start8 for your current VM and not fool with the new version of Parallels Desktop.
Parallels also promises that you can run Metro apps in windows on your Mac's Desktop, rather than in Windows 8's ungainly full-screen-only Start Screen mode. I guess the folks at Parallels took InfoWorld's suggestions for improving Windows 8, even if Microsoft didn't. However, you can't run Metro apps in their own windows within the full-screen Windows Desktop — where this feature would be most useful. Worse, I couldn't get this feature to work as advertised on the Mac Desktop, either. Parallels' PR shows multiple Metro windows on the Desktop, sized appropriately. But in my tests, every Metro app took a full screen (and required switching to what Parallels calls Coherence mode) — a major waste of screen real estate if you have a 27-inch monitor as I do.
There are some promising under-the-hood improvements in Parallels Desktop 9. For one, Windows apps can update while Windows is asleep, using the Power Nap mode in late-model Macs that allows OS X background app updates during sleep. Another is direct support for Thunderbolt drives, which can be directly connected to the Windows VM, if formatted as NTFS, FAT, or ExFAT. Then there's the ability to print straight to PDF from any Windows app's Print dialog box, offered by OS X for years. (Unlike some of the other Parallels additions, these actually work!)
Linux gets more support in Parallels Desktop 9, including new compatibility with the Mint and Mageia distros, as well as the ability to share apps between a Linux VM and OS X, as you could long do with Windows apps and OS X.
None of Parallels' enhancements are worth the upgrade price, especially given the futility of the key features, but at least they try to make your virtual life better.
What you should get: Parallels Desktop or VMware Fusion? I suspect few people buy new copies of Parallels Desktop or VMware Fusion these days (they're $80 each, by the way). Most users have probably been using one or the other for a while and are trying to decide whether to upgrade. I wouldn't pay money for VMware Fusion 6, and I would buy Parallels Desktop 9 only if I were using Windows 8 a lot. Most users can stick with what they already have.
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