like any website, does not perform optimally. >> reporter: and too many people trying to log in could still spell trouble. the administration said they'll be put in a virtual queue and will be given an e-mail with a better time to sign on. troubleshooters have been working around the clock, including at this command center in columbia, maryland. one expert we talked to said even if the 50,000 concurrent users' goal is met, how much time they're spending on the site could be a headache. >> so, the challenge isn't how many lanes do you have on the highway, it's how fast the cars can go down the highway. because if there's any breakdown, you'll have a big traffic jam and pileup behind you. >> reporter: republican critics like congressman fred upton aren't letting up. he's taking aim at the administration's claim that running smoothly for the vast majority of users means an 80% success rate. saying, quote, the situation is so bad that a 20% failure rate is the goal. >> and cnn's tory dunnan joins