Smaller ships - Mine Countermeasures Vessels and some patrol craft don't have stabilisers.
Anything above does though. They're okay, they work and they do attenuate the pitch, yaw and roll, provided the Officer of the Watch is on his/her game and know not to put the ship across the sea at low speeds.
Worst I have had is crossing from the Falklands to South Georgia in early 1994. Sixty, seventy foot swell from peak to trough in a 4200 Type 42 Destroyer. I've crossed Drake Passage a few times in HMS Endurance in 2005-2007 which is round-hulled and has no stabilisers, but a high-up 'Roll Reduction Tank' (which we had suspicions wasn't calibrated for the ships displacement, and the weather there simply does what the fuck it wants as it is the convergence of three transoceanic currents. Also was caught in a particularly nasty depression off Rockall in the destroyer in early 1995 where we were providing target calibration for the Victorious Class submarines. We turned back across the sea and the whole of the back end simply disappeared (according to the submarine captain watching on the targeting scope) under a vast wave which smashed the hangar door in and took the safely parked helicopter off its tethers into the front of the hangar and a member of the ships flight up one side of the hangar and down the other. Fortunately he managed to grab something before being swept out overboard, where we'd never have found him.
The weather = not to be fucked with
pommpey