It’s fair to say that people who like open source software won’t have much love for Microsoft’s commercial products. However, the reverse is also true – people who prefer commercial software are unlikely to try open source tools for the management of their Windows servers. Of course this means that Microsoft has an advantage with Hyper-V because people who use Windows Server will prefer Hyper-V as their solution of choice.
The most obvious competitor to Hyper-V would be VMware, and Hyper-V runs VMware close in user ratings. However Hyper-V solutions are generally a bit cheaper than the VMware equivalent and some people may feel that Hyper-V integrates better into the Microsoft software universe.
For some environments, of course, VMware might be a better option. It’s worth checking closely however because often Hyper-V includes advanced features and support for certain hardware as part of the purchase price, whereas VMware will require additional licensing.