The Jet Boots are a unique piece of equipment in that they do not offer any stat bonuses, but instead have the effect of increasing your character's movement speed. After much testing, it has been proven that while these boots DO increase your speed, the effect is so negligible that it is practically worthless.
The following table lists the times with and without Jet Boots. The test was conducted on Amber Garden 30th Floor (Tielle Boss Fight Room). The time is how long it takes to move from the very bottom to the top of the stage. A Jet Boots+4 and a Jet Boots+15 were used to prove that there is no difference with Fusion bonuses. All tests were conducted using Charme.
Only Charme and Griff can wear Jet Boots to increase their movement speed, however, it should be noted that this also takes a slot that could be used to boost other attributes such as DEF which may leave them more vulnerable in the more difficult dungeons in the game.