Running some rudimentary tests I noted the save process was a bit delayed. If I saved a file and immediately reopened it I'd see the previous version. However the overall the editing experience was great. I will definitely be using this in situations where previously would have used SP Designer or downloaded / modified / uploaded a minor change.
The new "Document Library Look" is beginning to round itself out and with features like this is going to make end users very happy! Would be nice if we could get a matrix of comparison with classic features so we know when to enable en-mass on customized portals.
Very slick editor. Nice colors & minimal feel. Line numbers enabled by default (take that Visual Studio)...
Surprisingly impressive auto complete support - given CSS3 + CSS4 selectors it's leagues ahead of SharePoint Designer.
If you right click you get a nice little context menu with the following options: Peek Definition, Go to Definition, Find all References, Go to Symbol..., Change All Occurrences, Format Code, Command Palette.
Command Palette Tools
When you click command palette (F1) on the tools menu you're presented with many additional commands. Although primarily formatting it's nice to be able to perform complex find operations etc.. Will have to explore this more going forward.
Overall this is a neat little upgrade that'll save developers time. SP Designer seems to have taken a turn toward the irrelevant and this is a much more convenient tool for quick updates & live repairs - in some ways it's superior so great upgrade by Microsoft! Happy SharePointing!