I have owned most, if not all previous generations of the Inova X1 and have been using the 2017 Inova X1 for the past few days. I like it.
The only visible differences between the new X1 and the earlier ones are the addition of a pocket clip and the lack of a lanyard hole in the tail cap. The new X1 is slightly longer, as shown in the photo comparing the 2017 and 2014 versions.
The new tail cap is a departure from earlier versions because it contains a forward clicky switch. Clicking it requires a very firm finger press exactly in the center of the rubber switch cover. That requires too much force for my liking so I activate the new X1 as a "twisty" like the prior versions. Perhaps clicking the switch will become easier with long term usage. That said, momentary action is easier on the new X1 than the older X1 because the rubber boot is softer and there is more travel in the new mechanism.
The older tail cap fits the threads on the new flashlight but will not activate the light.
The 2017 X1 has two brightness levels -- high brightness (125 lumens) followed by low (12 lumens). When powered by a Panasonic Eneloop Pro AA battery, the difference between the brightness levels is more pronounced than in earlier versions. My X1 seems to emit less than 12 lumens on low. It is low enough for close inspection work and to navigate indoors slowly without waking others.
The higher level is specified at 125 lumens which seems conservative based on how my sample appears. Ceiling bounce testing confirms that the new X1 is brighter than the 2014 version, though the tints on my lights are different from each other. The new X1 has a colder tint.
The light emitted from the new X1 is distributed differently than in earlier models. Older X1s cast a narrow beam with weaker spill which I find distracting indoors. Inova has increased the size of the central hot spot while placing more light into the spill area. Outside testing confirms that the 2014 X1 throws farther than the new version, but not by a huge amount. More noticeable is that the new X1 is better at illuminating a wider area.
I get just over 2 hours of decent brightness in the high mode when using an Eneloop Pro battery. At that point, the battery voltage drops below 1.0 volts. My new X1 draws 2,100 mA in high brightness mode and only 27 mA in low. Compare that to the 1,090 mA and 106 mA drawn by the 2014 X1, which was rated at 80 and 11 lumens.
The new X1 carries well in my shirt pocket. The new pocket clip is sturdy and isn't easily separated from the flashlight. The clip won't slide up or down the battery tube because it is fitted into a recessed channel.