Olbia is a working town and port, but with good facilities. It has a good, but fairly expensive marina suitable for wintering and liveaboards. There is also a yacht club (may find a berth), and a quay which is nominally charged for but is usually free which is very handy for the supermarket as it is in the centre of town.
Ashore: good provisioning. There have been reports of boats broken into when at anchor near the town. Near Olbia there are many anchorages to suit most wind directions.