Have you had the unfortunate necessity to use the IRS web site? It's actually fantastic. Getting logged in and authenticated is pretty weird, because you have to put in a credit card number or a loan number, but it's pretty good authentication for the audience.

The web site itself is snappy, well written, and I could do everything using Firefox on Linux. No "IE only" bullshit. Downloads are fast.

I'd give the IRS 10/10, except for the fact that I owe them money.

This is awfully reductive of "government." State unemployment offices are shit because no one cares. There are plenty of military and IC data processing web applications that scale just as big and just as reliably as Facebook and Google. It's a matter of priorities. There is nothing inherent about public funding that dooms you to a poor implementation.