We have been using Plesk for years, however we recently started using DotNetPanel as a VPS control panel for Microsoft Hyper-V.
I must say, im very impressed with the simplicity of it and the quality of the web interface. Not to mention, I think it may cost slightly less than Plesk, and it seems to have more features.
IMO, DotNetPanel is looking like the "best" Windows panel at the moment.
EDIT: forgot to mention, DotNetPanel has EXCELLENT support and Ive almost always gotten a response in less than 30 minutes by Email. In comparison, Paralells has probably the WORST support ive seen when it comes to Plesk.
Not trying to attack anybody, just sharing my experience.