Hi gberet and welcome to the Q&A Forum!
Congratulations on your purchase. I've owned two SD cameras, including the SD700IS, and love them.
Since the SD cameras the last few years function pretty much the same, I think my SD890IS Blog will give you some insights about suggested settings, features, etc. You'll have some enhanced features on the SD990IS such as the new DIGIC 4 processor and improved and expanded face detection technology. But the basics of use will be pretty much the same.
So take a look and if you have further questions, get back to us.
http://www.digicamhelp.com/camera-logs/canon-sd890is/my-sd890is-settings/