I don't mind saying it... I'm not pleased with the direction Mac OS has taken over the last few versions. Yosemite feels like a bit of a backwards step to me. It's as buggy as they come. The iOS integration seems to be more focussed on aesthetics than actual usability. iCloud feels like it has stalled and is a few steps behind the other market players. Basically I'm tired of it and having seen the Windows 10 announcements, and played with the preview a bit, I'm thinking I could be comfortable making the switch back to Windows sometime soon. The only thing that really keeps me in the Mac OS garden is the quality of 3rd party applications, and the quality of Mac hardware - most notably it's tight integration with the OS. One example of this integration that I'm yet to see on a Windows laptop is the multi-touch trackpad. Without a great trackpad that comes close to the usability of that of the Mac I just can't move to a Windows notebook.
So I'm thinking Windows 10 on a MacBook Pro will be an incredible combination. I hope Apple updates Boot Camp to support Windows 10 natively, including support for all the hardware - Thunderbolt, both GPU's, Retina Display, multi-touch, LE Bluetooth, and optimised performance of the already massive battery life etc etc.... I've used a virtualised Windows 10 preview on my MacBook Air quite a bit and it's fantastic, but without dedicated access to the hardware it's a bit hamstrung.
What do you think? Could Windows 10 be the next great Mac operating system?