The Random One said:
Also, I have a general rule that if a player rolls a 20... it works so wonderfully well everything ends up wonderful...
The flipside of this is when they roll 1. I'm actually thinking I need a more cruel critical error table.
The way I generally handle it is "Crit = Awesome, Botch = Interesting". Rather than impose outright failure, or worse, some kind of "fumble" result that makes the character look like a douchebag, I use "1" results as an opportunity to make the situation hum a little. Maybe some more guards show up. Maybe one of the engines on the airship blows out. Maybe your contact with the Thieves' Guild turns up at the bottom of a well. Whatever it is, it makes things interesting and ratchets up the tension without making the player feel like they fucked up or like their character is a pathetic loser.
I'm not saying characters should always succeed, of course they shouldn't. But there's a difference between failing because "oh, you rolled a 1 and cut off your own foot", and "oh, man, your Eagle's Talon kung fu is impeccable, but it looks like the Iron Mandarin's Golden Serpent style is better!"
Failure should be just as interesting and just as cool as success, if not more so. Indiana Jones is the classic example. If Indy were a PC in an RPG, he would fail nearly every roll. But notice how every time he rolls a 1, things get even awesomer?
So, that's my take on it. YMMV, of course.