A cap, when used properly, is effective in completing its task. IF your current battery and charging system can not keep up with demand, a cap will not solve the problem.
The proper use of a cap is to smooth out spikes in voltage in your system (it can also be a filter) Every amp has many small caps inside to stabilize the power supply. (some Zapco actually had seperate modules waaaaayy back in the day) Also MMATS added a cap bank to modified amps in SPL cars for burps.
Caps have a lower ESR so they can charge/discharge at a faster rate then a battery. They do not however ADD any power or reserve, they HOLD what is currently available.
So is the cap the answer to everything, no. When used correctly I would not call it a band-aide.
For more reading on caps, this thread was pretty good:
(i'll have to add link later, damn caraudioforum server sux)
Link added:
http://www.caraudioforum.com/vbb3/showthread.php?t=211794
Page two geolemon goes into good detail
95 Contour SE '01 3L 
