I picked up a $20 non-Sony charger - from a trusted brick & mortar store, not online. Can't test it yet of course, but I'm sure it will be fine. (Put that on the QC label. "Gruso is sure it will be fine.")
The problem with (most of) us testing these things is that we aren't equipped to truly test them. 40 different chargers might appear to do the job, but that doesn't tell you how clean or stable the supply is, or if it's doing damage (especially relevant for $5-$10 adapters, or anything bought from DealExtreme / Ebay etc).
One thing you can do is take a look at the information plate (or sticker) on the adapter and see if it says "5vdc regulated" or something to the effect of "5vdc @500ma". If it's the latter, then it will only be supplying 5v when the load is 500ma. Different loads will cause the voltage to fluctuate - not an ideal situation. If it says "regulated" then you have a better starting point - in theory it won't matter what current the Pandora draws, it will stay at 5v.
It starts to get shady when a power supply claims to be regulated, but isn't. MWeston had some horror stories about the units he went through before they found decent ones. If you have a multimeter you can test how well regulated it is by putting your meter on the plug, then dropping various resistors across the meter prongs and seeing how it affects the voltage readout. It's a pretty back yard method, but if you see the voltage dipping or spiking considerably, then it's not so well regulated.
I'm not a scientician, advice provided for entertainment purposes only etc
Come to think of it, I didn't even check if the one I bought was regulated. D'oh. I'll post details later.
