I've never had a problem getting Linux to work on a laptop. That includes Dell, Toshiba, Lenovo, even HP EliteBook (pain in the ass, but running LMDE quite nicely with NVidia).

Is the argument that those machines are bad because they ship with Windows?

I'm a huge hater of MS-anything (I can not quantify my hate of Windoze), but I don't see a valid argument to support overpaying for a slow System 76 machine when I can get my i7 Toshiba for $879 and put whatever OS I want (including a hackintosh VM).

Check out Zareason - the prices are pretty reasonable. I like buying from them because they've vetted every part of the hardware to make sure that any distro you want will work on it, and they'll find you the packages to install if the weird one you chose doesn't have them.

I actually do the reverse - buy a Zareason and install Windows on it for freelance projects that I need Windows to maintain, because I know that after the maintenance window has ended on those, I can throw Debian on it without issues.

The impression I get is that major Linux distros will work on almost any laptop, but if you want it to work well (good battery life, flawless suspend/resume, no issues with graphics drivers), you still need to think about your hardware.

I don't believe that Linux can ever go mainstream through just being installed on Windows machines: for most people it's just too much effort for too little reward. And for reasons both practical and principled, I want Linux to be a mainstream option. So I support people selling computers with Linux.