wrote:

I've got a lot of high-end audio and video equipment I've been using for
many years, in a variety of cities, and I DON'T have a power
conditioner; heck, I don't even have any surge suppressors! I've never
had a problem with most of my gear--at least, not problems that could be
attributed to power fluctuations.

Question is: are these things really worthwhile or necessary?

Unnecessary.

Cheaper cables (zip cord for speakers, analog cables from the 99-cent
store, digital cables from Monoprice) work just as well.

Extensive power conditioning is done by the power supply built into
each piece of A/V equipment, which contains a line filter (capacitors
and inductors - see www.cor.com) to stop high frequency noise and
minor surges, and electronic regulation to convert anything from
90-130VAC (90-240VAC for most newer equipment) into well-regulated DC
voltages, which are further filtered by yet more capacitors and
inductors.

Surge protectors can help because they provide insurance coverage for
surge-induced damage, but there's no need for expensive ones by
Monster (APC and Tripplite products are fine and much chepaer), but
consider geting a whole-house protector installed in your main circuit
breaker box for even more protection.

Active power conditioners are unneeded, but a battery backup may be
desirable if you like to use your A/V equipment during blackouts and
don't have a generator.