I feel like the computational (and, worse, legalistic) overhead for RPGs can detract from the fun of playing. So I wrote a simpler system that was based on that. Finding the middle of 5 d10s is something you can do (once you're used to it) in 0.25 seconds, so it's "immediately obvious" what the dice say. Adding 5 d10s takes about 1-2 seconds for most people, which is enough of a pause to break flow.

However, the real flow-breaker of RPGs isn't computation, but looking up rules in a rulebook to figure out how many dice of damage you take from a third-story fall before deciding whether to leap. This is one of the problems with formal role-playing systems... but, as always, the quality of the session has a lot more to do with the GM and players than the system itself.

But if I were to do a role-playing system now, it'd be based on Tarot cards (the 22 trumps). RPGs are more about interactive storytelling than about combat and number-crunching.