Before I had an iPod, I owned at least two other devices that played MP3s. First, a RioVolt SP90 that played data discs. Then, a 512MB thumb drive thing that cost like $50 and did everything an iPod did but on a small, buggy scale. Finally, I got a 20-gig iPod Photo—the one with a click wheel and no buttons. Suddenly everything has changed. A decade later, even seeing that little white box, with its satisfying heft and shiny chrome back, brings a weird wave of nostalgia for long walks with a now-obsolete consumer electronic device.

And maybe the time is right for loose-leaf, portable vapes—devices that use sub-flaming heat to leach the cannabinoids from crushed-up flower instead of the steaming liquid chemicals used in most vape pens—to establish themselves in the mainstream among the 150 million Americans who've tried marijuana and the 20 million who used it last month.

The original Pax is already a hit, of course. The first model came out in 2012 and was compared to the iPod by business magazine Fast Company. San Francisco-based Ploom, which makes the Pax, has sold a half-million of the devices, which inspired a trend story in the New York Post about "secret stoners." The original $200 Pax is nice, too. I've used one that's now 2 years old, and it remains in great shape except for the pop-out mouthpiece, which its owners say sometimes gets sticky with resin unless it's cleaned and lubed.

But after trying them side by side, it's clear the Pax 2 is a Doodah Man-sized step forward. Priced at $250, it's smaller, lighter and has a lithium battery that will last four times as long as the original. The oven—the little chamber you stuff with flower, which you are highly encouraged to run through a grinder so you don't have to wait while it vaporizes the tough stems—is deeper, and seemed to have a more consistent output.

The biggest difference, though, is the mouthpiece. I like the old mouthpiece—a plastic funnel that gives a very smooth draw—but the new one is a definite long-term improvement. The new model has a narrow slit on the edge of the black rubber atop the business end of the Pax. It's more discreet, super-cleanable and gets rid of the one breakable moving piece.

The big problem I have with the Pax 2? The accelerometer. There's just one button, on top, which you push to turn the device on after packing the oven on the bottom. Once the lights turn green, it's ready to puff, though the motion sensor will put the device into standby if it doesn't move for 20 seconds, then  turns it off after three minutes. The problem? If you walk with it, the motion sensor automatically keeps the device on. There's no way to turn it off, so I felt a disconcerting warm spot in my pants pocket on a recent walk.

But for the best method of imbibing marijuana I've yet encountered, that's a fairly minor complaint.