I just finished installing Windows Technical Preview 10061 on my Surface Pro 2. Installation went smooth, took about an hour to download the update. This was under the fast release, so if you have kept your updates to slow, you will not get this. I just spend few minutes using this release, so I would not be able to talk much on minute changes.
Hope you have noticed the back theme in the start menu, I liked it.
I could use the new Email and Calendar App. The best thing I could find is the ability to add Google Account to the new Calendar App. In Windows 8.1, we could not add Google Account to Calendar App. This was something I was looking for since I started using Windows 8.1
You can see that Email and Calendar App is integrated
I could see the Video Preview App too which is new to me, but I was released during the last build.
There some UI Tweaks, icons being modified, looks better than the previous build. If you want the ISO image of this build you can download it from here. Please note that this is not an official release. Do not install Windows technical preview 10 on your production machine, there are lots of bugs. I had to revert back to Windows 8.1 on my Surface Pro 3.
Will keep you updated on Windows 10 Technical Preview.