BARCELONA, Spain—At the Canonical booth at Mobile World Congress, I had a chance meeting with Mark Shuttleworth, founder of Canonical and spiritual leader of Ubuntu. I was actually at the booth to try out the new Ubuntu Edition of the Meizu MX4, a mid- to high-end smartphone, but all of the untethered devices had run out of battery—every phone, that is, except for Shuttleworth's.

"Can I borrow your phone for a while, then?" There was a brief pause while he processed the question, no doubt wondering what a perspicacious journalist would do with his phone, but then he nodded his assent and handed it over. We chatted for a while (he had some interesting things to say about the Ubuntu Edge, and I'm happy to report that he's an Ars reader) and then headed off for a meeting.

The Meizu MX4 is a shipping Android phone; it can be yours today for $450. Just like the Aquarius E4.5 that we wrote about a few weeks ago, Canonical is working with Meizu to make an Ubuntu Edition of the MX4. Inside the MX4 there's an octa-core Mediatek SoC, 2GB of RAM, Bluetooth 4.0, 802.11ac Wi-Fi, LTE support, and all the usual bells and whistles you'd expect on a modern non-budget smartphone. The 5.3-inch, 1080p display is pretty darn impressive for a $450 device. The MX4 isn't as thin or light as the latest Apple or Samsung superphone, but it still feels like a solid, premium, well-balanced device. It doesn't have an SD card slot unfortunately, but it does have a removable battery.

Rather amusingly, the MX4 that I played with today—again, Shuttleworth's—was running a "weeks-old" version of Ubuntu Phone (as in the OS). It was slower and buggier than the tethered MX4s that were on display in the Canonical booth. One of Canonical's engineers told me that they'd been trying to upgrade Mark's phone but hadn't yet found an opportune moment. (The tethered devices, though, were surprisingly slick.) There were quite a few slowdowns as I moved through the phone's menus—juddery, sub-60-fps stuff—but again the engineer told me that the software just hasn't been optimized yet for the new SoC. The CPU and GPU in the Mediatek chip should be more than capable of running Ubuntu Phone at full clip.

In terms of how it feels to actually use Ubuntu Phone, the best descriptor is... interesting. Unlike every other popular mobile OS, Ubuntu Phone is designed to work without a "home" or "back" button. Except for the power button or volume rocker, all of your interactions with the OS are through on-screen menus. To go back to the home screen, you swipe in from the left edge of the screen to reveal a list of your favorite apps/scopes and then hit the Ubuntu logo in the bottom left corner. Swiping in from the right side of the screen reveals the app switcher.

Ubuntu Phone has the usual apps screen and a settings menu, but most of your time on an Ubuntu smartphone is spent in a scope. In Android terms, these are essentially themed home screens (news, nearby, games, etc.) that are full of widgets. At the moment Ubuntu Edition phones ship with a standard set of scopes that are created/curated by Canonical, but the idea is for carriers/MVNOs to create their own scopes that are more applicable to their target audience.

Overall, I was pleasantly surprised with the MX4 Ubuntu Edition. Switching between apps was quick, and the camera was snappy (and surprisingly high quality). I would need a lot more time with an Ubuntu phone to see if I actually like the scope-based interface—it's quite different from any other mobile OS. The main issue at the moment, with the MX4 and with any other Ubuntu phone that comes to market, is that there are very few apps available. It's a problem that's likely to persist unless millions of consumers suddenly decide to buy an Ubuntu phone.

If you want a mobile device that is more open than iOS or Android, and you're OK with taking decent photos, using a Web browser, and consuming music and video, then the MX4 could be the phone for you. The Meizu MX4 Ubuntu Edition is targeting an April release in Europe, and Canonical expects it to have the same hardware specs and price tag as the Android version.

Finally, a word about the Ubuntu Edge: as we reported earlier in the month, some time between the Ubuntu Edge's failed crowdfunding campaign and the release of the Aquarius E4.5, the Ubuntu Phone OS lost its rather cool ability to become a desktop PC when docked. The good news is Canonical is still working on it—but you shouldn't expect to see such functionality in a shipping device any time soon. Shuttleworth let me play with a few tablets that had the magical feature enabled. When the tablet detected you had plugged a keyboard or mouse into the USB socket, the whole interface switched over to desktop Ubuntu, with all of your full-screen mobile apps becoming individual windows. It was actually kind of cool—but also, once Shuttleworth showed me that you could snap a mobile app alongside desktop programs, I couldn't help but be reminded of Windows 10.