This, for me, is the key thing. I generally find rules for drawing weapons to be effective when they mostly stay out of the way, but can still organically complicate ambush situations and force interesting tactical decisions.
For example, I like the D&D3 rules because you generally don't have to think about them: If you're ambushing somebody else, it's assumed you drew your weapon in preparation. If you run across a battlefield into melee, you can draw your weapon freely during the move. So the only time the rule comes up is if you're (a) caught in a melee unexpectedly or (b) changing weapons in mid-combat.
And that both feels "about right", but also provides just enough texture to give interesting results without giving a lot of hassle. (For example, just a couple sessions ago we had an outcome where the fighter dropped his bow in order to quickly draw his sword. When the party was forced into retreat, the fighter was forced to abandon his bow. That's interesting.)