I have heard arguments for using CAPS and arguments on how they are
useless
devices successfully sold purely on "hype".

I think they have legitimate uses, but I also think they're sold purely on
hype.


What is the general consensus of this forum concerning stiffening caps?
Are
they worth the money?

That's a subjective question. Are they worth the money to you? Well, those
that have solved their dimming headlights will swear to you they are. Those
that think they hear a difference in their audio will also usually say they
are. How can you argue with that?

Is it true that they unnecessarily drain your battery?

No.

Is there a good website to get information on how these devices work and
why
they are/are not useful?

The best car audio site on the net surely has something:
http://www.bcae1.com

Also, if there is a benefit to these devices, what constitutes a "cheap"
cap
versus a "quality" cap? I understand alot of answers to these questions
will
be opinionated, but I welcome them anyhow...

The single most important parameter (aside from of course the capacitance in
Farads) is the equivalent series impedance. This is usually given by the
ESL and the ESR. The lower number the better. Unfortunately, not all
manufacturers provide this information.