Like any pulse (normally used for beach hunting and nugget hunting), it's no secret that you can get coin-sized targets to over a foot, perhaps. The problem is, they're "too squirrely" to be used for the average coin/relic hunting site. They just seeooo sensitive, that you'll spend all your time trying to discern bird-shot, verses straight-pins, verses..... etc.... The discrimination on pulse machines is primitive. And yes, the TDI can be made to tell highs, verses lows, verses iron. But even then, it's still a sqquuuiirrreeelllly beast to use, if you think you're going to take it to a park, and find silver deeper than an explorer. And the minute you adjust the controls to knock out iron, and start trying to utilize the highs vs low ability, you will loose the fabled pulse depth. You will end up, in my opinion, with about as much depth as the Explorer, for coin-sized targets. So you might ask yourself, why then put up with the head-ache?
Perhaps if you were working wide open clean beaches, or nugget hunting, it would be more at-home. This may also go for CW sites, where persons intend to harvest everything anyhow, including iron, to insane depths. But if that is one's goal, I don't know that the TDI is more suited to strip-mining, that previously existing pulse machines. Heck, there's a Minelab nugget machine that can get a nickel to nearly 2 ft. deep

But you would never progress out 4 ft. x 4 ft. area, in even a slightly remotely junky site.