But I beg to differ. I can't comment on the TCW marks I and II, but I can say that the TCW Mark III is well worth using. Well made and finished, reliable and requiring little maintenance, it offers good service with minimal hassle. And it is reliable. The oft-repeated criticisms outlined above usually cite reliability, but they're really about safety. If there really were reliability issues then they were certainly sorted by the time of the Mark III.
Well, what about the safety? Granted, the TCW brake is weakest in high gear (and strongest in low). While this may not conform to the theoretical ideal, what really matters is whether or not it's powerful enough, in whatever gear. And that it is. And further, the chances of needing to brake suddenly, after you just happen to accidentally shift into neutral, should be remote. Shifting into neutral should be a rare occurrence. If it happens often there is probably something wrong with the adjustment or cabling. (Most SA hub problems are caused by external factors, rather than something in the unit itself, so perhaps you should consider learning how to adjust the gearchange. Don't worry, it's not hard.)
And most importantly, and at the risk of stating the bleedin' obvious, the above criticisms could only matter much if one rides without a front brake. If you are concerned with safety you won't be totally reliant on a rear brake – of any description.
So why should you care about the TCW, despite the doomsayers? To start with, it was made in the days when Sturmey Archer still cared about quality. The internal parts are finely machined and the case hardening long lasting (unlike the hubs made in the 80s and 90s), and it has a brass brake band (rather than the cheaper steel friction parts used in later models) for smooth and progressive braking. The TCW is well finished, with deep chrome plating, not just on the shell but also on the brake arm and left side dust cover. Compare that to the cheapo finishes on the current models.
The TCW also has the advantages of any coaster brake. For example, they require minimal maintenance. This doesn't just save your spare time; it also means you can rely on it to work its best when you really need it. In contrast, caliper brakes require frequent maintenance and are less likely to be at their best. There's no messy cable or lever to worry about. No adjustments. They don't wear the side of the rim, and they work when the rim is rusty, damaged, contaminated with oil or out of true. They don't get clogged up with road muck, and there's nothing to clean. And (for vintage bikes) they work in any weather – even the best caliper brake in the world is next to useless on a wet steel rim.
So take the criticism of the TCW with a fairly large grain of salt – they're really not that bad, and I think future generations will prize the few examples that survive their current demonisation. The TCW is a quality product, made to last. With a little care it'll continue giving good service indefinitely.