Albert features:
run applications;
open files;
open Chromium and Firefox bookmarks;
calculate math expressions;
search the web;
the modules are configurable: you can add/remove web searches, configure which files it should index, etc.;
supports fuzzy search (not enabled by default - it can be enabled individually for each module);
you can modify the actions taken by pressing the modifier keys;
configurable hotkey, maximum history, maximum number of proposals, subtext for selected/unselected item, etc.
ships with many themes by default.