It's still much slower than, for example, Sublime Text. A search for a single letter [1] in a ~5,000 line file occurs instantly in ST, but takes about 1 second in Atom. It's not much, but it's very significant from a UI point of view.

[1] I know such a search is ridiculous, but both editors perform search-as-you-type, although atom does attempt to delay that if you type quickly enough. Anyway, it's just an example to demonstrate the speed difference.