ATmega168 + 20 MHz crystal, timing issues?

Hey guys, I just wanted to know if I loaded a program onto the ATmega168 and then put it standalone on a breadboard with a 20 MHz crystal, will I run into timing issues? In other words, will delayMicroseconds(100) still delay for exactly 100 microseconds?

Some things will be off. I forget which functions are affected.

Okay, so I found what's different, http://www.arduino.cc/en/Hacking/OtherHardware

Can someone explain how they're different though? Will delayMicroseconds simply be off by a multiplier? How does analogRead behave differently? If I have to recompile the bootloader does that mean I have to get a programmer?