Although it's similar to the budget version offered for just over 10 bucks, I've been using this Futaba BR-3000 despite it being priced considerably higher (and despite them being our competitors in the servo business). Why on Earth would we offer a competitor's battery tester? Easy, it's because this is a very fine product and you have to give the Devil his due! Anyway, I consider it the better of the two we offer and while it's no skin off the nose which you prefer, I carry one of these in my flight box.
ProTip: connect a 2-wire JR-style lead for NiCd/NiMH packs (which typically don't have a balance connector for measuring individual cells) at the 2-pin port. With regard to lithium-type packs, e.g. LiPo, LiIon, LiFe, and super duty LiFePO4 (A123) because they have a balance connector, then making the connection to the tester with it gives you more than just total pack voltage. This is because you can measure the voltage of each cell in the pack at the individual pins of the connector. Arming themselves with this information (voltage of the individual cells) is the 'how' behind pros staying ahead of weak cells (for determining when to put a pack out to pasture).