First impression was that the start page could use a bit of UX love. Looks a bit messy and too grey.
The first thing I noticed different from C2 is that I can finally use touch completely in C3 without any extra 3rd party apps. C2 has terrible touch/stylus support. So this is a big plus, since I'm usually developing on a Surface Pro 4, on my back in the Sofa.
Everything else seemed very familiar but a bit more polished. Except for the layout and event sheet tabs that looks out of place with the rest of the UI design. My OCD working with UX/UI design kicks in on small things like this.
Two finger zooming in layout is jumpy/doesn't work. Scrolling works with one finger which feels a bit odd. Usually that's a 2 finger command in most apps.
I couldn't open any of my C2 files in PC but some worked on Mac. Nothing happened when I clicked open. No errors, they just didn't load.
Besides from that, and considering it's beta so far I haven't noticed anything major.