I think the real systematic flaw is that Saga allows the use of skills vs defenses for major abilities. Otherwise, I think it's pretty solid.
When comparing between Saga and 4E, I think Saga seems a little... simpler.
That can be appeal for some (as others have pointed out - you do stuff like throwing grenades, firing your blaster, and you don't have any special effects involved. For those that want something more complex, they play a Jedi. The powers of course are more complex and interesting.
4E has the same complexity for everyone, and it is a little higher then the Saga standard for non-Jedi. That can be a problem, since sometimes you don't want to dwell on the "rulesy" stuff, and focus more on the rest of the game.
What I find pretty interesting (and it was pointed out for me especially in Mike Mearls recent podcast) is how the defined roles in 4E change the (combat) gameplay.
In Saga (and also 3E) everyone plays the same game of hitting your foe hard. The Noble is possibly the exception, since he is more about aiding his allies to hit hard (similar to the 3E Bard). Basically, you have a lot of Strikers and one Leader. Jedis might have a secondary role as Controller, but not that much.
In 4E, you clearly play your roles - the Striker is the one that still plays 3E and deals damage. But the Defender is really the one to take all the damage, a game nobody really could or wanted to play in 3E, and the Leader is all about helping the Defender to take that damage and helping the rest to hit. (In that, he's like a Bard with better buffing spells - or a Cleric
). The Controller doesn't really care about how much damage he does directly, but mostly about how he can restrict the enemy - either they can't escape, or they aren't in a situation where they can't attack effectively.
But I think that Saga makes a pretty good job at mimicking the Star Wars action. There are no real roles in Star Wars - everyone of the characters holds his blaster or light saber when it comes down to it. There is no one that would be able to "take the heat" - they are all shot at, and nobody tries to expose himself as a target. There are Duels between antagonists and protagonists, but they are 1:1, meaning no Striker vs Defender distinctions, and the 2:1 encounters (like Obi Wan and his master against our "Tiefling Sith"
) don't make a distinction between someone striking or defending.
Of course - Star Wars characters don't include a real soldier. (The closest is Boba Fett, but he doesn't work in a team - and Janos fate might tell us about trying to "defend" against a Jedi
)
So, whatever I'd do with Star Wars, I would probably not try to import the roles directly, but I would probably introduce a more generalized power system, and use the 4E system and powers as an idea-giver, but probably trying to avoid much of the board-game focus and remove dailies and some rider-effects. I think Star Wars doesn't gain much with daily mechanics (maybe aside from hit points or healing surges), and to throw a bone through the simulationists.
The board-game focus is probably a hindrance for newbies (especially if we consider that there aren't that many Starwars Minis, or are there?), and the rider-effects can be replaced with minor action powers. (That probably become stronger without the n[W] power component)
