Karma was always intriguing, at least in theory. You get a relatively cheap mobile hotspot and data, but it's open to anybody. If somebody near you uses it, you'll get free data added to your plan. But the best part of the Karma system isn't the scheme to try to get free data, it's the way you pay for it: flat-rate data without any monthly plan. You pay for what you use and nothing more. If you leave it in a drawer for six months, it doesn't cost you a penny.

A clever system, but there was a big hangup — back in 2013 when it launched, it relied on Sprint's doomed WiMAX network. But in September 2014, Karma announced a new model was coming with LTE for $149, due out in December. Delays, as they often do with small hardware companies, kept the device from shipping until just this week. Now that it's here and I've been using it for a couple of days, I'm still more intrigued by the theory than the execution. But I'm very intrigued.

A well-built little puck

The Karma Go is a svelte, well-built little puck that I wasn't afraid to chuck in my back pocket and forget about. It's smaller than most of the other mobile hotspotsI've used, and seems to be well-built. A mobile hotspot is a simple tool, and the Karma Go is honest about that. Karma says that it lasts for about five hours of continuous use — but I got slightly less than that. Part of that might be because I let it go into sleep mode overnight instead of fully powering it down.

But that desire for simplicity means that, feature-wise, the Karma Go is pretty basic. Unlike devices that are loaded up with an LCD screen, the Karma Go makes do with a single button and four LED lights. Three indicate signal strength and one is for battery life. But there are times when you just want to get more info out of your internet gadget: just how many devices are connected? Am I on LTE or 3G? Just how much time do I really have left before the battery konks out?

If you want answers to those questions, you'll need to install the Karma Wi-Fi app on your Android or iPhone — or visit Karma's website from your computer. There, you'll see what devices have been connected and how much data they use.

But Karma's app doesn't let you do everything you might expect. For one, you only have a few options for naming your Wi-Fi network. Karma defaults to using the name you enter when you sign up for the service — something I wasn't really pleased to find out. The other big thing you can't do is set the password for your mobile hotspot. It's always open to anybody who wants to use it.

That's part of Karma's model for getting new customers. If somebody joins your Wi-Fi network, they are asked to create a new Karma account to get online. (They'll get 100MB free to start.) If they do, you'll get some free bonus data. Karma says that there's no way that somebody on your Wi-Fi network will be able to use it to sniff out your internet activities.

I'm not particularly interested in Karma's business model here, and if I had my druthers I wouldn't let anybody jump on and share my connection — even with LTE, a mobile connection can be a perilously scarce resource.

Sprint's network has fallen behind

Which brings me to the elephant hidden inside this little gadget: the Sprint network. In New York, I've found that Sprint isn't nearly as good as either Verizon or AT&T. It's absolutely useless in my office, for example, even though the Karma Go shows full bars (er, full dots). When I do get proper service, speeds are slower than what I can get with other networks, too. So the idea of sharing a signal I already don't fully trust is bothersome. Also, since it's on Sprint, you're out of luck if you want to use the Karma Go outside the US.

That open Wi-Fi network doesn't just work for anybody who sees it, of course. The sign-in method uses a "captive portal," which is one of those websites that make you log in before you can access the broader internet — you've probably seen them at hotels or Starbucks. Luckily, most phones and computers can handle those just fine with a quick pop-up. Once a device is recognized, I've found I don't have to re-enter my credentials every time I connect. But a captive portal also means that the Karma Go won't work with any device that can't log in via a website — so if you're hoping to use it with an Apple TV or a Chromecast while you're at a hotel, you're out of luck. Karma says it's working to find a way to support those "faceless" devices.

And yet! Despite all of those hurdles I'm so happy with the idea that I don't have to pay a monthly fee for this thing that I'm willing to live with all of those problems. I don't like the annoying captive portal, the open Wi-Fi signal anybody can use, the aggressively simple design, and above all Sprint's network. But I know that each one of those annoyances are necessary to make the Karma Go's payment plan work. Karma needs the captive portal and open Wi-Fi to entice new customers. Above all, it needs the super cheap rates that Sprint charges bulk customers.

Aggravating technical limitations and basic features, but I love it

It all means that I can have LTE data for around $14 per gigabyte. That’s a little more than I’d like — Google’s new Fi network only charges $10 per gigabyte, for example. But then again, I don’t have an extra monthly data plan sucking down my bank account. I bought a Karma Go to use it, but I also bought it because it won't punish me if I don't use it. That's rare — maybe unique — in the wireless industry. I hope it succeeds enough to make the next Karma Go arrive on time and on a better network. That’s the Karma Go: aggravating technical limitations and basic features, but I love it.