I think you need to be very selective with your traps. For example, having a trap in the middle of nowhere is the best way to grind a game to a halt. All of a sudden, the PCs are searching everywhere for traps just in case.
I prefer traps to be on obvious things such as doors, chests or rooms that just have that feeling that some huge trap is waiting for a foolhardy adventurer to set it off - you know the ones. With all of these, there should be a pay-off for success, be it advancing further or finding loot. However here are several alternatives:
- Raise the DC into the above take 20 range but make the pay-off worth the consequences - mixing it with an encounter can really get the blood pumping, particularly if the trap adds an ongoing element to the encounter.
- Design traps that will be set off if the PC loiters in a particular region, thus forcing them to make a single check and then get out of the way. If they take 20, they find the trap literally by setting it off. Again though, don't overuse this otherwise you make taking 20 redundant and it should always be an option. Give the players cues so they can get a feel for the situation they are in and whether taking 20 might be the better option or not.
The other obvious element is just because you find a trap, does not mean you can automatically disable it. You can't take 20 on disable device (or at least a take 20 is considered to have rolled everything from 1 to 20 thus most likely causing a fail). As such, there is still a chellenge there for the party.
As for taking 20 with other options, I think there are limitations. You can take 10 with most actions but not 20 if failure has consequences. Otherwise, I would not worry about it too much with these elements, let the heroes find what they seek - what they seek may not always be good.
Best Regards
Herremann the Wise