For just $349, the Nexus 5X is a pretty great smartphone. For $199, it's a steal -- and starting today, that's the price you'll pay if you buy it straight from Google.

There is one important catch, but it's not nearly as significant as you might think. To get that $150 savings, you have to activate the Nexus 5X on Google's own Project Fi cellular network.

Why is that not a big deal? Three reasons:

Project Fi doesn't lock you to a contract. You can leave whenever you want, and suspending your service is as easy as tapping a button in the Project Fi app on your phone. We've confirmed that there's still no contract with the Nexus 5X deal.

Once you leave, the Nexus 5X works on any US carrier: AT&T, Verizon, Sprint or T-Mobile.

Signing up for Project Fi is cheap: just $20 + $10 per gigabyte of data. You pay that $30 upfront -- but if you don't use that first gigabyte, Google will credit the $10 back to you.

Here's the fine print. And before you ask, you no longer need an invite to sign up for Project Fi. As of today, it's open to anyone in the United States. Here's how to sign up.

Now playing: Watch this: Getting to know Google's wireless service, Project Fi

Of course, Google is probably hoping you won't leave. It's hoping that its superior cellular carrier experience and impressive coverage -- Fi automatically hops between T-Mobile, Sprint and Wi-Fi networks -- will convince you to stay.

According to Google, the Nexus 5X deal will run until April 7, while supplies last. You can take a look at my review of the Nexus 5X to help you make a decision.