GT ores that spawn in oceans also spawn in rivers.
Railcraft has geodes in oceans that contain extra diamonds/emeralds/lapis and possibly other things.
BC oil ocean biomes will be gone. The desert ones are so rare they might as well not exist at all, especially when you'll likely not have many vanilla deserts.
Other than that nothing of importance should be gone.
Oil bothers me a bit. But it's not the end of the world lol. But yeah it's amazing how nice the world is without an ocean.