As good as any other coaster really is. I would still say inferno, galatica or swarm are the best first upside down coasters.
Anyway, now that I have conquered my fear of upside down coasters, the next major thing is more intense flat rides that go upside down (not spinny flats which start to make me feel ill). Thus, as I'm planning to visit Chessington soon, what does Ramses Revenge feel like and does it make you feel ill?