I’ll be the first to admit that I don’t do much testing outside my development environment. That includes my main machine and the array of virtual machines I browser test within.
I like the author’s solution of grabbing a cheap netbook to keep on hand. The barrier to entry is comparatively low at a couple hundred bucks (keep in mind we’re going after a lower caliber machine here) and it can act as a good throttle for your high level animations and styles.
The other throttle to keep in mind is that higher speed Internet service you’re paying for. Not everyone has a pipe that fat and keeping a close eye on the way your documents are actually painted on screen can be a real eye-opener. You don’t necessarily need a separate machine for that, as you can throttle your own bandwidth with something like Charles, a fantastic Web debugging proxy.
Running Charles on your testing netbook might be a great overall picture of ‘worst case scenario’.