I'm so excited for this: an IDE with first-class support for Hack? Yes please! My only reservation is the last time I used Atom, it was pretty slow, what's it like nowadays?
Similar experience - Atom on my home Macbook Pro is quick and snappy and an overall nice experience to use, but on a similarly powered Windows 7 work laptop it is noticeably slower to the point of being unusable. Last time I tried it on the Win7 box was about two months ago.
I use it every day. Mostly good, but clearly slower than ST3. My main gripe is that it is painfully slow at editing with multiple cursors. Multi-cursor edits that ST3 wouldn't hiccup at freeze up atom long enough that OSX asks if I want to kill it.
Slow compared to ST, but usable, and some buggy behavior at times, but mostly usable (I use it for JS and Rails dev across numerous projects)
Slow and buggy text editing!
text editing is mostly ok for me: biggest bug is the full screen bug on OSX (it'll create a modal on the wrong full screen, but when you switch, the modal disappears, but still blocks the UI - only solution is hard kill, meaning you lose progress if the modal was a Save dialog)