Why accelerate my Amiga you ask?
It makes it more bearable to use especially in graphic and productivity applications, the basic A1200 is a very underpowered machine. The Amiga is a multitasking computer which allows you to run more then one program at the same time, more programs require more CPU power and more memory (RAM).
So, basic A1200 comes with 2MB RAM and 68020 14MHz CPU, it's enought to run simple games and some software, but if you need more, then you need to upgrade and make it faster.
Paint programs with filters will benefit from more CPU and RAM to speed up rendering, any 3d software will benefit greatly.
The 68020 is equivalent to Intel 386SX, the 68040 is close to 486.