I have been looking for a good universal system for some time now, and I heard some buzz about EGS and thought I would give it a look. At first glance, it reminded me strongly of Savage Worlds, classic Cortex, and the combat and power system evoked Legend/Runequest to me. There was a nice mix of simplicity in character creation and general rules, but with enough tactics and crunch in combat and magic to appeal to gamers who want more depth. The Qualities of characters seem especially interesting, as they can simulate all sorts of advantages and disadvantages by using pretty basic mechanics.
The core mechanic is add an attribute due type with a skill die type, roll, and attempt to beat the difficulty number (7 being the standard). One minor issue for me is that I feel eight attributes are far too many and some of them seem either unnecessary or redundant, but its not a deal breaker and is an easy fix if you feel the same. Hero points, which are the game's resource for important characters, are very important to the system and figure strongly into the previously mentioned Qualities of characters. Like classic Cortex, these points seem pretty vital to success especially when the difficulty of the task is high.
Combat feels tactical but fluid and quick, and while it has many of the options of Legend/Runequest, it does not feel as complex. As written damage is fixed and it not modified by anything except Hero Points and called shots, but there is an option to roll it randomly. Armor is treated as extra health points, and when those are depleted further damage is taken directly from health. This is a decision I feel is a bit odd, and is justified in the rules as pieces of armor being loosened or knocked off. After combat armor points are restored, but it doesn't feel like even heavy armor is terribly useful except for absorbing a few more points of damage. There is an option in the book for treating it more like ablative damage resistance, and I prefer that to the standard rule.
Special powers feel like a mix of Savage Worlds and Legend/Runequest, with a general system covering everything from sorcerers to superheroes but powers can be manipulated and tweaked on the fly depending on the situation. There is a good range of powers and options in the core rules, so there is a lot of potential for different character types for different genres.
There is also a good section on running the games for GMs, and a solid list of adversaries. The basic book seems more focused on fantasy and modern games, but a science fiction supplement is forthcoming. Basic rules for designing various racial and cultural backgrounds are also in the GM section and there are good examples of stock fantasy and sci fi species.
Aside from a few minor quibbles, the Entropic Gaming System seems like a good option if you are looking for a universal system with a simple mechanic but potential for depth and complexity. And even the quibbles I have with it are easy fixes if you feel the same, and at $5 it is well worth a look.