James, this exactly mirrors my own experience. I deliberately had them be transparent to the players, hidden behind plot, which meant that they weren't actually fun or exciting for anybody - including myself. Making them an explicit sort of mini-game turned out to be a blast. I'll admit to being surprised by this.
Again, right there with ya. Several things changed my mind:
1. It was simple to add it into the Character Builder, so nobody had to remember the math.
2. It made things more fun for the players, instead of less fun. That's the big seller. Everybody likes it when daily powers hit, myself included.
3. There are finally enough cool, flavorful feat options available now that making players take a boring mechanics-feat to stay effective seemed sort of cheap.
4. If it turns out to be a horrible idea (which I don't think is likely), I can easily revoke it or transparently add a point or two to certain monster's defenses when I need to. It's pretty low risk house rule for me, with far more upside than downside.