It is great.
Also, while free-as-in-beer, its licensing status is currently proprietary... a significant turn-off for the audience that Microsoft is targeting with this. Every rumor suggests that they'll be open-sourcing it eventually, and that the process just takes awhile to work its way through legal, since Visual Studio Code borrows its editor code from their commercial Visual Studio Online product. But it's still an open question.
Overall, I am "intrigued-and-cautiously-optimistic" right now (its startup time and responsiveness are MUCH faster than Atom's!), but I'm not ready to switch over full time just yet. I'm looking forward to seeing where they are with it by early next year, when all of the other cross-platform .NET stuff is ready for general availability.
Surely launch time is basically insignificant for a text editor which you might only launch a few times in a day?
Back when I had a mid-2010 mac mini, there was a noticeable lag between resizing an Atom window and the contents redrawing - when sublime and gedit were fine with the same files.
That was a comparatively slow computer; someone with a higher performance computer probably wouldn't think the performance was all that poor. I can only assume the Atom developers find the performance tolerable.
Still, it reminded me of the old joke [1] that the speed of software halves every 18 months.