I'd have no problem riding a walmart/kmart/dept store bike today. Hell I've beaten people on full carbon trek 5200's with my $350 specialized mtb with 2" tires aired up to 70psi.
I had a guy keeping up with me for a bit on my roadie and he was riding a touring bike with a trailer with TWO little girls sitting in the back.
Lance armstrong could probably win a Cat5 race on a dept store bike if you replaced the tires and gave the thing the proper tune up.
My old stock pacific toy store bike with big knobbies inflated to 30psi used to go down the hill at 30mph; the same speed as my current specialized mtb commuter with high pressure semislicks.