Threat in Tabletop RPGs

I was a bit intrigued when I saw a post on Penny Arcade about the Edge of the Empire beta of Fantasy Flight's new Star Wars title.  Of particular note was the dice mechanic.  It appears that the game is played with the standard polyhedral dice well-known to D&D players, but with a twist -- they are custom dice, in the same way Dragon Dice were.  They're measuring success using a threat mechanic, which is an interesting twist.  I'm not certain I'm particularly sold on custom dice, and I haven't tried the beta, but threat is a mechanic I've been considering implementing in my own games.

In my own forays into running tabletop titles, I've largely been a purveyor of Cthulhu as a system.  4th Edition D&D had marks, 3rd had Intimidate checks, and movement was limited by attacks of opportunity in 3rd, but other RPGs have largely had an informal threat mechanic consisting entirely of balancing two things:

• Equaling out damage and resource consumption among all players
• Making certain the opponent felt dangerous each turn without killing players

While this is fine when players are doling out roughly equal amounts of damage, it means that there is never an incentive to pull punches, and never a moment when players particularly are endangered based on their own ability to slaughter enemies.  The end result is that players largely consider NPC actions based entirely on DM Fiat, and that there is absolutely nothing they can do to change who the enemy is targeting, so why bother doing anything other than the most optical amount of damage?
This is largely a challenge that has been considered solved by CRPGs, because of the ease and availability of calculations on the fly.  As I'm certain you're familiar, the amount of damage in turns into a threat, that then must occasionally be reduced or superseded by "high-threat" moves.  The brief reports of this Star Wars beta have me thinking that a threat mechanic that is clear to players and is largely reactive to their choices is actually viable.  Here are my thoughts regarding threat mechanics:

1. Critical success gives you top priority of threat.
2. Degree of success gives you increased threat.
3. There should be artificial threat generation and "detaunting" methods.
4. There is one tracker for boss mobs, and one tracker for "trash."

Provided it doesn't place an enemy in a known disadvantage, the enemy will attack whoever has the highest threat.  This creates a fairly simple system in which threat is tracked in the same way initiative is, and leaves less of the groans related to GM fiat. What're your thoughts?