We have had two Stac servo-type AVRs that bit the dust. Both of them had servo circuit failure due to input voltage spikes. Servo-type AVRs may be good on output accuracy, but it is typically slow to respond to fast and significant voltage increases and brownouts.

For that matter, I've moved to using UPS's with built-in relay-type voltage regulation on all my sensitive equipment (home server and network equipment, entertainment center, bedroom TV, and of course, our family PC). Relays may not be as accurate with output (typical accuracy of +/- 10V on the output), but it responds instantly to transient rise and drops of the input voltage. And if it goes beyond what the internal AVR can correct, the battery kicks in, totally protecting the equipment.

Equally important is to make sure that your equipment are properly earthed/grounded. The surge suppression circuit inside most equipment, including power strips, UPS, or AVRs with built-in surge suppression, relies on the ground pin to dissipate power surges, typically as a result of nearby lightning strikes or when a nearby heavy inductive load starts up, etc.