I've been running it for ages on a mbp with 2.6GHz i5/8Gb RAM. It's lightning fast.
Very occasionally it will appear to be hogging CPU - typing is slow and it might hang for a couple of seconds when you're navigating around. This only seems to happen when I've had it running for days if not weeks without a restart. I just restart it and it's back to being lightning fast.
I really like Atom and would be pretty upset if it stopped working well for me, so would be curious to know what kinds of things people suspect cause it to have issues.
Is it just that my machine is powerful enough to not notice, and it's only really a problem on less powerful machines? I don't run many plugins, and installing many of these tend to bring it down? It runs well on OSX but not other platforms?