Iceland is a young volcanic island where the landscape is the whole point: waterfalls dropping off old sea cliffs, glaciers running down to black beaches, steam rising from lava fields. Most of it is reachable from the Ring Road, and the south coast alone can fill a week.
The season changes the trip completely. In June the sun barely sets and the highlands open for walking. From September to March the nights are long enough for the northern lights, and ice caves form under the glaciers in the coldest months. We plan with private guides and Super Jeeps in winter, when driving yourself is harder.
The honest caveats are cost and weather. Iceland is expensive day to day, and storms can close roads with little warning. We build in spare days and never plan a glacier walk the day before a flight home.