I remember having Rune use the thunder claw for a while to preserve his TP, but eventually he has such a huge reserve of TP that it almost never runs out. (And yes, I giggled every time I typed "TP.") The rest of the tech gear I was bleh on, because I did fine without it.
I didn't know about any of the items with tech abilities in PSIII until I replayed the games a couple of years ago. I think I got that information through the LP of the game. The game's easy enough without them, so I don't feel like I ever missed out on using them.
The tech items in PSII are definitely useful. I was never without the two Storm Gears at the end of the game if I was playing with characters like Shir or Hugh. The Snow Crown plus Amy's Sashu together make damage minimal and are perfect against really strong enemies like dragons and fiends, especially if you're playing with Hugh and don't have him behind a shield.