Building a bike?

I was wondering about the pros and cons of buying the individual
components of a road bike and assembling them myself. I'm interested
in a fairly cheap bike anyway (in the $600-$800 range), so at that
rate, is it really worth it? Is it cheaper than buying pre-assembled
at that level? Also, does it require a lot of familiarity with these
types of bikes to be able to effectively assemble it, or is it really
simplistic with the right set of instructions? Do they ride better
pre-built than if you put them together yourself? Any information
would be greatly appreciated! Thanks in advance!