I've used the McDaniel/SonicTronics igniters for years. As Phil said, the new one is terrific with NiMH battery.
Agreed, the new version has three important changes from the original - the clamp part is much sturdier, the battery is NiMH instead of NiCAD and much higher capacity, and probably most important, there is no longer a sliding contact for the center post. Used to, there were telescoping brass tubes, the inner with the wire from the positive terminal soldered to it, and the outer, which moves with the spring-loaded center post contact. The inner contact made a sliding contact with the outer, so the current path has got this sliding contact of relatively high resistance, and could change when it got dirty/oily/corroded, and as you shook it, sometimes losing contact entirely. The new ones have a wire connected directly to the center terminal, coiled around to take up the movement, so the resistance is effectively zero all the time and doesn't care if its dirty or shaking. That's why it glows brighter and more consistently.
One issue - you don't want to use the old-style NiCAD charger with the new battery, you need the new charger to properly charge it. I think the old one gave about 100 mA and the new one is 300 mA ( I will check tonight). If you keep using the old one, the battery will still charge, but it will take much longer and it will never entirely charge, because at some point the 100 mA drops to nearly zero as the terminal voltage approaches the supply. The new charger drops from 300 (or whatever) to 250 or so, because the voltage of the battery never gets near the supply voltage under load.
The failure mode of the battery is also different - when new, the battery can sit for months in your toolbox without charging and still be fine. Eventually, like it fell off a cliff, the self-discharge will go up and it won't retain a charge for more than a few days even without use. It will still work but you will have to charge it every day before use. You don't want to charge the new ones every day or before every flying session, because it will overcharge them, only charge it when it is clearly depleted.
Brett