Yeah, the rad suits coming on ubiquitously for the first warp entry was a nice touch. They wear them later in the film, perhaps in part just to stay prepared for when the engines get fully revved. At first encounter, Scotty is still in his regulars, but it looks like helmets might actually be needed aft along the shaft. After Ilia is taken, they go to full emergency power for a bit. Now, Scotty seems to think that the rad suit is a good idea. The red rad suit is also a nice touch. They also wore them a lot in TWOK, so it would seem that they were really needed even after the post-TMP proper shakedown, though I guess one could also argue that since it was a training vessel by then, they were merely observing the extreme protocols for training purposes, and/or staying prepared against the possibility of cadet blunders.