These things affect what plans you qualify for and how much they'll cost you. It also does work, it's not as if they built something that nobody will ever use. Some millions get through each day, and long before the 6 month enrollment period is over, there won't be anywhere near this kind of load to handle.
It's only been 3 days. Imagine if Blizzard Entertainment wrote off World of Warcraft on day 3, when it was also barely usable with almost exactly the same number of people trying to get online. That'd be ridiculous.
If it weren't day 3 and the site was working, you'd never wish what you just wished for. Nobody would want a system where you have to choose a plan then wait an unknown amount of time to see if you're approved, interact with a bureacracy to correct conflicts between what you provided and what they found in those other systems after-the-fact, have to re-make all your decisions. That's essentially what we have now, except you're interacting with the government instead of a private insurer, and it sucks. What they're giving us instead is the simplicity of online shopping applied to health insurance -- a listing of plans you actually qualify for, the true price you'll pay for them, and online signup on-the-spot.