I hope you did try the Touch mode in Windows 10, the one with the fill-screen Home Screen. Didn't you?
I spent the day after I installed the 9926 build, fiddling with various and sundry things in it. It all started being not so good early on with the enormous 'start' screen as part of the start button. Took up about 3/4 of the screen on the Yoga 2 Pro. There is a hack to get it back to the one that was on previous builds, but that is all that is, a hack and may or may not be there going forward.
The switching from desktop to tablet mode is all very manual and not at all intuitive.
Bottom line was that all my apps and such worked, most of them became more 'fiddly' to use because you are never really in what was considered the 'modern UI' of Win8/8.1. W10 is all about the desktop and that is where you are at, even when you think you aren't.
That said. These are all growing pains as MS struggles to get W10 in shape to make people want to get it. The tech preview is buggy and some things either don't work, or work in a fashion that you don't like. It most definitely should NOT be on your daily driver. Way too many uncertainties.
One of the things that is very irritating isn't caused by W10, but is still an issue. And that is app data. I have a utility to backup and restore app data for the 'modern' apps, but it takes time to do so switching from W8.1 to W10, even on the same machine is not as useful as it could be IF I want to use that data. It would be so much easier if 'modern UI' apps just saved their data on OneDrive and other machines could use that data without user intervention.