While it's not the end-all, be-all test, I've found ESR to be a very reliable way of testing electrolytic capacitors, especially in switching power supply applications where they are high failure items. ESR becomes critical at higher frequencies and at least 95% of the bad electrolytic caps I've found have had high ESR.

I've never used that particular tool though, I bought a Capacitor Wizard about 15 years ago when they were the only one around. These days there are a number of simple analog ESR tester circuits floating around.