Along with invincibility, Vexx will also have the ability to kill enemies just by touching them. Vexx will also be able to run faster (although it'll take a bit longer to reach the top running speed). The Suit is often used to smash crystal containers which have Wraithhearts in them. Without the suit, there is no way of freeing the trapped heart.
However, the suit also has its disadvantages; due to his heavier weight, Vexx's jump height will be decreased, and he will be unable to climb walls as his weight will drag him down. Vexx will also lose his ability to swim, and will sink to the bottom like a stone. While underwater while using the Rock suit, Vexx will have infinite oxygen until the Suit's timer reaches zero. As well as that, Vexx will jump higher than normal.