I'm working in little extreme environment; edit files on remote filesystem (external network, surely) that is mounted on my Laptop thru ssh(aka. sshfs). Regardless why I'm doing like this, also though its cumbersome responsiveness, it's fairly edible when I'm using Sublime Text 2.
I tried on Atom after reading this post, but it turned out to be somewhat painful to me; Atom seems that it doesn't cache directory structure so efficiently. Every time I expand a folder on Tree View, the UI froze for a short time, 2~3 seconds, maybe fetching file system info. Yes, it's because I'm using remote filesystem. But Sublime handles this more efficient, at least it doesn't freeze every time I expand a folder, so less painful.
I think Atom is hell nice for free, and my story is trivial that might be enhanced someday, but it would be helpful to someone at this time.
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added on 8/26/2014
Recently, I changed my laptop from Macbook Air 2010 late to Macbook Pro 13" 2013 late. It has likely 4 times faster CPU and much enhancements in performance. I want to mention my opinion is about in the case WHEN YOU MOUNT REMOTE FILE SYSTEM. (using OS X Mavericks, most recent version of Atom, FUSE 2.7.3 / OSXFUSE 2.6.4 / sshfs 2.5.0, and remote system is Ubuntu server) Eventually, UI freeze gets pretty shorter, but it is still there. Specifically, to open a folder with many folder/files in it and index it is requires certain amount of time. Also, if you expand a folder full of files, it just falters. (when collapsing the folder, it doesn't)
According to @EliDuenisch , it seems not happen on Linux Mint. I'm not sure but it might be from difference between OSes. Surely, if you work on local file system, you don't have to care about this issue at all.