I've been using Tomato-USB on Asus hardware for several years now... the current Asus firmwares aren't bad though the early ones were pretty horrible. I actually prefer Tomato and similar options, I used openwrt for my home office (routerstation pro) for a few years as well. Being able to run third party software is essential for security updates given that the manufacturers rarely offer more than 1-2 updates and almost never after the first year of a product introduction.

Tomato, dd-wrt, openwrt and the like allow me to control my hardware and use it for the life of the hardware, not the year of updates the mfg gives.

I also like Tomato on ASUS hardware, but as far as updates go, it seems little-to-no better than using stock manufacturer firmware. There is no central development project, and there is no one who ensures that new updates work on existing hardware. It seems like a few people put together some builds that work on what they have, toss them over the fence, and everyone else is left scrounging for what works on their particular hardware.

And are you really going to experiment with building it yourself when you're talking about your Internet router? What do you do if it bricks?

I've been thinking for some time now that the only sensible way forward is a device that runs plain Debian stable, something Raspberry Pi-like, with a USB dongle or two and a plain Ethernet switch. That way, keeping up-to-date is as simple as `apt-get upgrade`. And with a few SD cards, one can easily keep multiple working system images, clone them, and swap between them for testing and upgrades. This situation in which it's even possible to brick a router seems like primitive savagery and madness.

But, not having a DD-WRT/OpenWRT-compatible router, maybe I'm just missing out...?

Dunno... It's pretty hard to brick the router beyond recovery via tftp... That said, I'm no expert on the issue... I've been using the Shibby Tomato-USB releases myself, but tbh don't update as much as I should.

Looks like there's no third party release for the RT-AC3200 yet, though the mfg release is modified tomato.