The ultralisk's attack is hardly impressive for its cost and high tier. Its main advantage is durability, staying power and fear. The ultralisk may lead an attack and draw the first volleys of defensive fire allowing more of the lesser zerg units to survive and close to attack. The ultralisk's relatively slow speed requires some planning to get it to the front rank before the attack. Its large footprint may hinder it and its allies at choke points in addition to making it difficult to re-position once caught in a melee.
The ultralisk, along with every other unit, was visually upgraded in StarCraft: Remastered. Carrying over its kaiser blades was difficult, as it was difficult to gauge how sharp they were meant to be based on the original sprite.