One caveat: the free plan lasts only 12 months. Once that is over, you'll be forced to opt into a paid plan.
In addition to the tiers, customers can select two different speed levels. Lightspeed is up to 1Mbps down / 384Kbps up, and Warpspeed is up to 10Mbps down / 1.5Mbps up. Switching between the two takes a simple visit to NetZero's website (although it can take up to 15 minutes). These settings can be used to conserve you limited data, particularly on a low tier.
This assumes, of course, you buy either the NetZero hotspot ($99.95) or the USB stick (Windows and OS X-compatible, $49.95). The hotspot provides a wi-fi signal, just like setting your smartphone or Verizon iPad up as a hotspot. NetZero's offers support for up to eight other devices.
We had access to a pre-release model of the NetZero wi-fi hotspot. The device is using Clearwire's WiMax service (which, as you probably know, is technically 4G but far slower than LTE and being dumped by Sprint for that reason).
In fact, NetZero's 4G Hotspot is the same model as the Clear Spot Apollo, and the USB stick is the same model as the Clear 4G Mobile USB modem (manufactured by Ubee).
The NetZero 4G Hotspot, which we tried, has only two buttons, for power and for turning on / off sound notifications.
As far as service goes, ClearWire's WiMax doesn't work too well in our area. We had to keep the device close to the window to get an effective signal. It's unclear if that was related to the signal or something else. If the device was taken outdoors, it had a much clearer signal.
We also had an issue with our test device: we couldn't power it on. Turns it it was on, but we couldn't get the screen to activate, nor could we power it off. It was hung, but we couldn't figure out a way to reset it.
Eventually it ran out of battery power and came back to life.
If you're in an area with good ClearWire coverage, and use little data, this device could be a good choice. However, if you lose a lot of data, it should be noted that ClearWire's own service plan for the same basic device (remember, we noted it was the same) is $50 for unlimited data, without a contract, as well.
A bigger problem for both services is that ClearWire's WiMax service is limited in availability. Be sure you check the NetZero (or, basically, ClearWire) coverage map before signing up for either of these services.