I always thought the take 10 and take 20 rules were fairly easy to understand.
Take 10 is just doing your average everyday effort, when you aren't really worrying about anything else. About the only time you can't take 10 is when you're in combat. The part about being "rushed" is stupid, just ignore it. You can't "rush" most actions, they take how long they take. When taking 10 you take just as long as usual, you just don't need to roll.
Take 20 is just like take 10 except it takes 20 times as long, and you can't do it if there are negative effects for failing. So climbing up 30 feet you can't take 20 on, because if you screw up, you'll fall. You can take 20 on picking a lock, though, since there's no negative effect for failing to pick a lock.
It's really very simple.
Now, as for actually using these, yeah, a lot of my friends forget they can just take 10. When someone calls for a <blank> check, the automatic reaction is to pick up a die. This happened the other day in an epic campaign we were in. My friend with 30 strength was trying to open a stuck door, and is notorious for rolling crappily. After two failed attempts with bad rolls I was like "dude, just take 10". He did and opened it without incident.
I think people think about taking 20 a lot more often than taking 10. Taking 20 is the "crap, this thing is really difficult, I guess we have to waste the time and do it until we get it right". Taking 10 is the "this isn't really an obstacle, so just kinda walk on by" thing. And people forget they can just take 10 instead of having to roll.
-The Souljourner