Are universal power supplies for laptops worth it?

"The usual take on this is: They may work but if anything goes wrong, then don't expect your warranty on the device to hold. At least that's what the manufacturer will tell you.

The power just specifies how much the power supply is able to supply but it won't affect how much your laptop is going to use to charge the battery.

As for the voltage, using 18 or 19 V should work without damaging anything, but be sure to try with 18 first :-)"

Be aware that some laptops will go into minimum-power mode unless they are connected to a power supply that properly identifies itself to the laptop as The Right Kind; this is very often a problem with Dell units, and reportedly can be an issue with some other brands as well. When shopping for a "universal" unit, ask the store if you can hook it up and make sure that the laptop accepts it correctly before you buy; if they don't, it's a good bet that they already know that your unit won't work right with what they're selling... or that they aren't sure that it will work, and don't want to stand behind it if it doesn't.