All advice should be taken with a grain of salt. Interpreted and adapted to a particular set of circumstances. Anything 37Signals says is no different.
Personally, I've found a lot of wisdom in what JF/DHH have said. Does everything they say apply, literally, in 100% of situations? Of course not. But there is/was a whole lot of traditional/oldskool advice out there that is too extreme in the other direction, and what they advocate is a refreshing alternative that DOES work for them, and DOES work for other folks.
Personally, I've found a lot of wisdom in what JF/DHH have said. Does everything they say apply, literally, in 100% of situations? Of course not. But there is/was a whole lot of traditional/oldskool advice out there that is too extreme in the other direction, and what they advocate is a refreshing alternative that DOES work for them, and DOES work for other folks.
As always, YMMV and caveat emptor.