People have mentioned most of the points here, however, there is one slight variation of one point and one different point to be made in favor of Quickdraw:
variation: If you're wielding a two handed weapon, make more than one of your attacks, and drop your foe, you are ordinarily done with your actions whether or not you had more attacks. However, if you have quickdraw, you can quickdraw ranged weapons and throw them until you run out of attacks then put your thowing hand back on the two-handed weapon. No more wasted attacks.
Other point: Quickdraw enables multiple weapon strategies to be more effective at high levels. A character with 36,000gp and change to spend on weapons might buy one +4 equivalent weapon like a +1 keen holy greatsword. A different character might opt to buy more specialized weapons--a +1 wounding guisarme and a +1 ghost touch, undead bane heavy flail, for instance. With Quickdraw, the second character can always pick up the weapon he wants to use against that particular foe rather than being limited to the weapon in hand. (It's not necessarily a great strategy for fighters who benefit a lot from specializing in one weapon, but paladins, rangers, barbarians, and multiclass characters can benefit a lot from it).