If you want to attack in the surprise round (assuming combat starts with weapons sheathed) then you need quickdraw. Otherwise, you can only move+draw. Note that a charge is specifically not a "regular move"--you don't get a free draw while charging.
If you're a Polearm fighter and want to get your full attacks in (or keep your mobility) then you need Quickdraw. Otherwise you can only draw a sidearm and attack once.
If you're a TWF fighter and want to get in a full attack the same round you draw then you need quickdraw. Actually, all fighters that want to get in a full round attack (all iterative attacks) when they draw will need this feat.
If you like to use Rapid Shot with daggers or other thrown weapons and are not ambidextrous or you have something in your other hand, then you'll need Quickdraw.
If you're an assassin, you'll want Quickdraw. Here's why:
Assassin Player: I walk up to the target.
DM: He nods to you in a friendly way, then goes back to his book.
Assassin Player: I attack!
DM: okay, roll init. It's a surprise round, so you get a partial action.
Assassin: (rolls a 4). Right. I, uh, draw my weapon.
DM: Okay. Surprise round is over. He rolled a 5 for his init. He yells "Help! Guards!", draws a weapon, and attacks.
Assassin: Boy, I sure wish I had Quickdraw. Then I could've drawn and attacked (with Sneak Attack Dam) during the surprise round.
If you use a bow or other two-handed missile weapon, you'll want quickdraw. Then when you're forced into melee you can ready a shield (move-equivalent), draw a weapon (free), and attack all in the same round. Otherwise, you'd have to spend one full round (two move-equivalents) getting ready for melee.
Most DMs will let you Quickdraw scrolls, potions, or pretty much anything else that can be snatched with one hand.
Quickdraw is incredibly useful.
-z
