The Gladiator Class Star Destroyer is a quite a decent ship. It is especially useful when given the "Demolisher" upgrade. Being able to put yourself where you want before you shoot a second time makes putting large holes in your enemy's fragile spots rather simple.
Even without significant upgrades the Gladiator Class is still a good ship. The plethora of black dice on each hull zone has allotted the Gladiator Class to shred any Mc30c frigate that gets too close. Nebulon Bs will become easy targets when you use the Gladiator Class correctly. Point your front hull at its sides and end its life swiftly. I typically use at least one Gladiator Class in all my imperial builds. Please comment your opinions on the Gladiator Class or how you use it in battles.