I have my A620 set in C(ustom) mode: AIAf off, Iso Auto (when needed i change it to 50 or 100, max. 200), 7 MP superfine, the rest default settings. EV -1/3 standard, -2/3 on sunny days and + -0 indoors. With this settings i take 80% of my photos, the remaining 20 % i take in Tv, Av or M mode. I have tested the vivid colour option, but IMO the pictures are sometimes too unnatural. But you will have to test, which settings are the best for you.
mg66