First, let me explain how Fi works. It's essentially a unique WiFi-first service that prioritizes calls and text messages to be done over WiFi and not data. Whenever you're around trusted open WiFi hotspots, the phone will automatically connect to them thanks to a feature called WiFi Assistant (It won't do so with paid WiFi connections unless you've already set them up beforehand). If you're not around WiFi for whatever reason, Fi will switch to either Sprint or T-Mobile depending on which has the stronger cellular signal, a feature that's unique to Fi, at least as far as US carriers go. The hiccup here, of course, is that Fi is only compatible with a few phones. At launch, it only worked with the Nexus 6, though now its repertoire has expanded to both the recently released 5X and the 6P.

Even before I could even order my Fi SIM card, I had to decide on a phone number. As with any carrier, you can port over an existing number or opt for a new one. But there's a caveat if you're a current Google Voice user. If you decide to use Fi with a non-Google Voice number -- say, a primary phone number or a new line altogether -- then by signing up with Fi, you're forfeiting the use of that Google Voice number forever. That's it. No take-backs. For me, keeping my Google Voice number was pretty important -- I sometimes use it as a secondary number for work -- so I decided to assign my Fi service to it. Which is fine, but I wish I didn't have such a conundrum over whether to keep my Google Voice number alive just so I could use Fi. [Ed. Correction: We're told that you can actually transfer that Google Voice number to a separate Google account if you want to keep it, so all is not lost.]

Once that was squared away, the process was pretty easy. (Or so I thought: My first Fi SIM card was defective, so I had to exchange it.) I received a SIM in the mail, which comes with a handy green paper clip with which to pop out your phone's SIM card tray. I removed my existing card as instructed, downloaded and launched the Fi app from Google Play, and followed a few short instructions to get the service going. It took a few minutes, but before I knew it, I was up and running. The app is also where you can track your data usage and check your monthly bill.

Speaking of that bill, that's really where the value of Fi comes in. For about $20 a month, you get unlimited calls, unlimited domestic and international texting and WiFi tethering. From there, you'll have to cough up about $10 per GB of data, which sounds like a lot, but if you're using WiFi most of the time, that shouldn't be a big deal. And, best of all, if you're particularly stingy about your data use, Google will actually refund you the money for any unused data.

Oh, you also get free data coverage in 120 countries. That means that no matter where you are -- Canada, Hong Kong, London -- you'll pay $10 for each GB of data.

In a way, Fi was tailor-made for someone like me. As a homebody, I rarely leave the confines of my house or office, and am almost always within reach of a WiFi network. In the course of six months, I've barely touched my monthly 2GB data allotment and frequently receive money back each month from unused data. I found myself paying a little more than $20 a month for Fi, which is the least I've paid for a cell phone service, ever.

Compare this to the basic wireless plans from the four major carriers. Assuming unlimited talk and text and a basic 2GB data plan, they run about $55 a month for AT&T; $50 for T-Mobile and Sprint; and $65 a month for Verizon (with 3GB instead of 2GB due to how Verizon's tiers work). Those prices often don't include tethering or data coverage in international cities and, of course, none of them refund money from unused data like Fi does. In every case, Fi wins out in price and affordability.

Fi really comes into its own when using it over data instead of just WiFi. For the most part, I didn't encounter much service disruption when doing so. The icon on my phone would just switch from WiFi to a cellular symbol and I could never really tell whether I was on Sprint or T-Mobile. The only way I found out was by using an app called SignalCheck Lite that told me what carrier I was on. I did discover, however, that I was unable to surf the web and talk on the phone at the same time when I was on Sprint, which could be because of the carrier's slow move to Voice over LTE.

I tried making calls over WiFi and seeing if they would transition well over to a carrier if I wandered out of WiFi range. I found that while the calls did eventually transition over to the cellular network, there were at least a few seconds where the conversation fell silent -- neither my friend nor I could hear each other -- and then all of a sudden we could chat again. I also noticed that once the calls are on the cell network, they don't transition back to WiFi even when you're back within WiFi range.

It's also worth noting that while I did save money on Fi, it probably won't be a great service for everyone. There's no unlimited data option, for example, as you're expected to sip at your data and use WiFi the majority of the time. If you coughed up money for even a 10GB plan for Fi, that would cost you something like $120 a month, which isn't that different from most carrier plans anyway.

That said, if you have a Nexus phone and you're happy to live with just a few gigabytes of data a month, then I see absolutely no reason for you not to give Fi a shot. It's fast, reliable and best of all, incredibly affordable. And seeing how much more improved the recent crop of Nexus devices are, I would even recommend you at least look into buying one just to take advantage of Fi, especially if you were in the market for new hardware. Of course, this all depends on whether your particular city has Fi service, but if it does, give it a shot. You just might be a convert.