Complex Checks are something I really liked from Alternity that I actually ported over to d20, well, right away.

So I'll agree that has a general leg up.
I need to put together a full-on probability-conversion for d20Modern, showing what the complex-check DCs should be for common DCs listed in the various skill descriptions.
I've been working with d20M alot and, honestly, it causes me to actually respect the decision not to use complex checks.
As Buzz points out, if the game is 60-80% skill checks and is going to feature alot of bomb-defusing action, then a complex skill check like that is a great thing.
But what if it isn't? You can model Sam "The Bombmeister" Johnson with a single throw and a high modifier. "Yay, you easily defused the bomb!" but you can also model John P. McBadass, ACTION HERO, who snips the right wire at the last minute with his toenail clippers while hanging upside down. "I did this once while training for shadow ops in Cambodia."
I.E. one difficult roll is easier to overcome with a lucky roll and spending an Action Point/Die, while complex checks generally favor failure and high skill bonuses.
That is, I think, a major reason for the "Can't Fail This" class abilities. IIRC, they tend to guarantee consistent high rolls for complex checks the class will often be making. I.E. fixing the fact that those complex checks are usually weighted to "the house".
Just a thought I had. D20Modern seems really well suited to doing alot of different genres, because many genre conventions were just left out. I'm working on a wild-west-type game and was in the process of creating a complex (and totally sweet, mind you) system for duels and quick-drawing your gun, etc etc. And I realized ... it's already there. If you want to be good at it, you take Quick Draw and Improved Initiative and have a high dex and spend an AP on your initiative roll. I didn't really need a whole new system, just a little section talking about it.
Some things I do change, of course. D20Modern is "action hero" focused and doesn't do the whole: "Ah! Y'shot me." one-shot-drop like westerns do, so I cranked the MDT down to 10 and added an ability that can force an MDT on a flatfooted character under certain circumstances (and spending an AP). I.E. The guy that loses the draw will have a reasonable chance of ending up at -1hp.
But that, again, is the point. You don't want my wild-west genre convention in your high-flying action game. It's more gritty than would be fun ... unless gritty is what you were looking for.
SC2.0 is an absolutely superb Superspies game. Top of the line.
That very fact starts to trip it up when it goes to do other things.
--fje