Not only opinions, but agendas as well. I'll bet that some definitions would help. It would be helpful if somebody would define just what, exactly, is in a "power conditioner". Is it an isolation transformer? R/C network? Magic dust?
Like someone said, the best thing you can do is buy an outlet tester for $5.00.
I wouldn't want a "glorified surge protector" that wasn't able to be re-set. Using a Furman with SMP (which is able to re-set), or any other "power conditioner" where the outlets are still hard-wired (through a protection device like an MOV) can't hurt anything, because they don't limit current. Of course, as someone else pointed out, if you mis-use it (by turning your amp on and off with it) you will cause damage. The better ones (they used to be cheaper, but so were Fenders) provide lights, a power strip, surge protection with a re-set button, and a common ground, which is the reason they reduce hum. Some supply a voltage reading, which is also helpful. IME, 15 amps is enough for most bars and restaurants, which usually only have 15-amp circuits anyway (at least the little dives I play at). Fortunately, that's all most amps need. And your rack plugs in and you're up and running in less than a minute, if that's important to you.
Major venues will have a sub-station of sorts to provide clean power for the stage and most top-flight mobile installations will also supply a regulated power source (but not with Furman single-space units).
The problems I've run into are usually outdoors where there isn't enough power coming to the "stage", or where the bar owner decided to have it wired by somebody to pay off a tab.
And that's when the outlet tester is your friend.
