The number of users affected is unknown, but the list of laptops mentioned in that thread is pretty varied, and it makes Ubuntu unusable for those folks.
I know OSS needs to be more attentive to aesthetics, but let's not forget that "Ew, I just can't STAND these fonts" is a different kind of unusable from "I tried six obscure workarounds listed in a bug report, but none worked, so I installed a different OS." Using a laptop exclusively as one's primary computer is extremely common these days. If showstopper bugs are tolerated on laptops, the perception of Linux viability for non-tinkerers is going to regress back to five or ten years ago when it was common to encounter bugs like this in a desktop install.
Poor sleep/wake stability was the single biggest reason I gave up on Linux. I was running Ubuntu on my HP nc8430 and had to rush out the door so I closed the lid and didn't wait to make sure it went to sleep properly. I tossed my backpack into my car and when I came back a few hours later I found out the machine never went to sleep. It got so hot that the enclosure actually melted and warped. Probably lucky it didn't catch on fire in there. Amazingly the machine still worked but the physical damage to the enclosure prevents the lid from closing properly and it won't sit flat on a desk anymore.
Not to take away from either of you, but I had a very similar problem with Windows XP on a Dell Inspiron 9300. I would open my insulated laptop backpack, at least once every few months, to find a computer too hot to touch and the smell of baking foamcore. I have not had that problem with Ubuntu, and it has been running on that machine since 7.04.
It was compounded by a hot day and being inside a backpack. The problem I was having at the time was a hard lockup of the system on sleep maybe 30-40% of the time due to the ATI graphics driver. My best guess is once the machine hard locked ACPI was unavailable to auto-shutdown the machine once the CPU passed its threshold so it ran until the battery died instead.
For what it's worth, the battery lasts half as long in Ubuntu than Windows (Dell Studio XPS 16). Also the fan is always on moderately loud even if I am only browsing the web or the lid is closed, and it heats up under the trackpad more than Windows to a degree that is annoying.
I know OSS needs to be more attentive to aesthetics, but let's not forget that "Ew, I just can't STAND these fonts" is a different kind of unusable from "I tried six obscure workarounds listed in a bug report, but none worked, so I installed a different OS." Using a laptop exclusively as one's primary computer is extremely common these days. If showstopper bugs are tolerated on laptops, the perception of Linux viability for non-tinkerers is going to regress back to five or ten years ago when it was common to encounter bugs like this in a desktop install.