I liked the 1e psionic system. Or at least, I loved what it tried to do.
The basics were that it grafted a class-less spell point magic system onto the mainframe of AD&D. With that extra power came horrible vulnerability to some really awesome monsters.
The basic campaign arc of a character with psionics was that he was the most powerful character in the party until he met up with a psionic monster, at which point his brain would be turned to goo. A classic live fast, die young paradigm and a wonderful exemplar of AD&D's "balance schmalance" attitude (which I share).
If the DM ran the rules as written and a quarter of all wandering monster rolls after psionics or related powers were used were done on the psionic table, walking around with a psionic character was like having a "GOOD FOOD HERE" neon sign pointed directly at the Abyss.
It painted a nice, grim Cthuloid picture of the D&D world, and also did a lot to explain why there weren't magic factories, magic hospitals, etc. due to the fact that so many magical spells attracted so many foul creatures.
To me, it was just part of the whole kooky fabric of 1e. Sometimes I use it, some times I don't. But I always find it interesting and imaginative. I liken all the peripheral sub-systems in the 1e core to the Beatles song catalog. I like pretty much every song the Beatles recorded, but I'm not going to try to sit down and listen to every song in one sitting.