Compared to other solutions it's very limited. The guest additions (for sharing files between host and guest, shared clipboard, dynamic resolution, etc.) only work for Windows 7 and up (some people need to virtualize XP and such). The sound does not work for me with my external audio interface, I can only use the integrated audio in my Mac.
There is no supported way to backup and restore your VMs (but there is an intriguing "read only" mode, you just need to change your workflow a bit to make use of it).
On the bright side, it's very lightweight, fast, secure and it's on the App Store, so no trouble with licensing, and it does not litter your system with kexts etc.
All in all it's too limited for my use case as of now (and I only use VirtualBox) but it has potential. It may be right even in its present form for some people, though.
