They are typically heavier than a conventional derailleur setup but not by a massive amount. It is rotating weight which is bad but it's hub weight which is much less bad than rim weight.

To me tank like means that they just keep on going. You don't have a vulnerable derailleur hanging out there to get banged up. Because the chain is working a constantly straight driveline wear and tear is MUCH less. The things just keep working.

Adjusting Shimano ones is dead simple from my experience. Really you have to be a special breed of idiot to be unable to adjust the shift cable once you're shown how. Old Sturmeys can be a little tricky but they pull so much cable per shift that I don't think cables are really an issue once they're setup (unless the cable rusts into the housing or something).

We've had Sturmeys in the co op that had been lubed with excess cooking oil that gummed up, an amazing idea by some enterprising kitchen staffer. Flushed out the mess with some concentrated degreaser and re-lubed and that bike was rolling again, like new. Well as new as the decade old chain would allow it to sound (we wanted to replace it but the guy didn't want to, wasn't broken to his ear).

If they can get the weights and price for a 12+ speed one down to competitive with a decent gear setup and market a high quality STI lever to match I wouldn't think twice about running one. For now derailleurs still win for cross in my mind but if you want to have a bike with gears that's almost as simple and reliable as a singlespeed then IGH is a very reasonable option.