I think psionics is the scab that D&D can’t stop picking at. What began as a set of optional rules from the first edition AD&D Dungeon Master’s Guide has been revisited in every edition since with varying degrees of success. They tend to be either poorly integrated into the core mechanics, the worst offender being second edition’s Complete Psionics Handbook, or presented as simply an non-Vancian alternative magic system. Neither approach has been very satisfying. As magic in D&D has become more diverse with the addition of core classes like sorcerers and warlocks, psionics has had to work harder and harder to justify its existence. Still, I am always interested in new psionics systems when they come out, so I made sure to check out the PDF.
The first thing that stuck out to me at this most recent attempt had nothing to do with the mechanics. Rather it was tying psionics so closely to the Far Realm. To some extent this makes sense, after all the monsters that are most likely to be psionic have always been aberrations. Less successful to me was their attempt to explain why psionics are more common on some campaign worlds than others, which boils down to the “weirder” your campaign world is (Dark Sun, Eberron), the more influence the Far Realm will have and the more common psionics will be. If anything this simply seemed to highlight how out of place psionics tend to be in a normal D&D fantasy setting.
As for the crunch, these rules present the Mystic class and two orders: The Order of the Awakened and the Order of the Immortal. These are roughly analogous to Psions and Psychic Warriors from previous editions. The core mechanic is that a mystic has a certain number of psi points that can be spent on certain class abilities or to activate disciplines. Your Psi points completely regenerate after a long rest, which makes book keeping easier but does little to differentiate it the way magic works in D&D 5e. Disciplines don’t have levels but can often be manifested to greater effect by spending more points. This used to be a mechanic that set psionic characters apart, but nowadays most spell casters use the similar mechanic of getting more bang out of their spells by casting them with higher level slots.
Of the two orders presented, I think the Order of the Immortal has more to distinguish it from the other base classes. The class it reminds me most of is actually the magus from Pathfinder. Both have a full range of weaponry, midrange armor, midrange hit points, and a pool of points they can spend to boost their martial prowess and enhance their weaponry. Neither is ideal as the main fighter in a party, but both can function as an off-tank with a little extra versatility to make up for some squishiness.
Personally, I didn’t quite find enough to differentiate psionics in these rules to convince me that they are a necessary addition to the game. It is important to note though that these are presented as an early playtest of the psionics rules, not as a finished product. One of the things that helped make D&D 5e such a strong version of the game was the extremely open nature of the D&D Next playtest and the willingness of Wizards of the Coast to listen to player feedback. If they follow the same template with these rules, maybe there is hope for psionics yet!