I've seen things about this, but I'm not convinced there's enough value in going to great lengths to replace that particular piece of equipment.

In the case where the terminating equipment is a small box that exposes ethernet, with no routing or otherwise interfering the function of my own router, I think it's good enough. An argument could be made for the all-in-one devices, like saving some power.

I get the geek factor, and it's one of the reasons why I run my own router, but for this specific bit, which needs to be fairly well integrated with the ISP's network, combined with their usual abysmal support, I think it's a better bet to just leave it alone.