Impact drivers stress-tested

Which is the best 18v impact driver? I already bought the Milwaukee one [Amazon, tool-only] because I have Milwaukee batteries and am shackled to the vendor, but Todd from Project Farm (previously at BB) reports it's the best one anway.

Todd's tests are exhaustive and merciless ("Not all impact drivers survive this showdown") but picky, focusing on a handful of premium models and the cheapo Harbor Freight one. The Harbor Freight one is fine, but obviously not in the same league as the others and it still costs $70.

After watching the exhaustive tests, though, I've decided that what I really want is a digital tachometer, as used to test each driver's RPMs. You point it at whirly things and it tells you how whirly it really is. No idea what I'm going to use it for, though.