dreatica
Dev
Flash is not a must have for me, although its always good to have one.
Same goes with the official update thing.
Nexus S and Galaxy S hardware is quite same. So when Nexus S gets ICS officially, it will be available for Galaxy S unofficially.
Galaxy S is good in terms of super amoled screen which is superb, plus mmc option, fm radio, great dev support @xda forum Only thing missing is Camera flash. Ignore that and buy Galaxy S.