The servers can be really, really fast -- but in any shared hosting environment, it depends on what's happening with the other accounts on the server as much as what is happening with your own code, as well as how much traffic is being handled by the network in general at the time (you've probably noticed that your own internet connection is a lot slower in the evening between about 7:00PM and midnight than it is during the rest of the day). And there will always be server maintenance to take into account.
You can move to a paid service (even the low-priced Illuminated package here) where you're sharing a server with far, far fewer other accounts, but there can still be slower periods (especially when people's daily or hourly cron jobs are running). The only way to get blazing speed all of the time is to have dedicated server resources. VPS plans usually have a minimum chunk of the server that is yours all of the time, plus a reserve pool of resources that everybody can share (so you can grab a bit more memory or processor time on the odd occasion when you need to). And you can get hosting (dedicated VPS, dedicated servers and colocation) where your machine is your machine and the only thing you're really sharing is the network -- but all of these improvements cost money. And that's not just an x10Hosting thing -- the hosting has to be cost-effective for the host.