Totally worth it. If you've ever had to fix an audio cable, you need one of these. At the price, they are less than half of similar products from other places (with the exact same chip and internals, just a different casing!). Sure you need to know about your cables and have to think about what the LEDs are telling you, but that's OK, that's why you bought the thing anyways.
The test tones are useful, but a little harsh sounding. They are simply a square-wave output so they doesn't sound that great, but do an OK job of setting levels and doing audio sanity checks. Intuitive interface. The main switch turns on easily in a bag (simply fixed with a piece of Gaff tape).
Otherwise, no issues. If you are an audio tech. Get one now. Avoid the embarrassment of your musicians or speakers not being heard because of a dead XLR cable. Check your entire lot and fix or replace them now. It's great because you can test any combination of connectors on your cables (ie. XLR to 1/4 phone, XLR to XLR, TRS to miniphone, etc, etc). Oh, and the intermittent test feature is fantastic! Even helps you find RF noise on long audio-snake runs.