Hm... Idk but the last time I talked to my sister and her other Filipino exchange students to Japan, they said their foster families were far more impressed with their courteousness and formality.  I think as a non-native speaker of any language, it's better to stick to formal approach to reduce the risk of being misunderstood and having rude impression. ;)

Green: I'm not saying that this is a replacement for studying formal Japanese, or that people should be using casual speech all the time instead of polite language.

However, if you want to understand how people speak on a day-to-day basis, then you will have to know this stuff. Whether or not you use it depends on the situation. If you're talking to a stranger or an elder, you should (probably) use polite language, but if you're talking to your friends in polite language, you will sound really weird.

I agree with Mike on this. Being a beginner (fast learner, but still a beginner), I naturally started with what Western scholars think is Japanese, to put it bluntly. With real, day-to-day Japanese, I have NEVER encountered such a level of politeness, even if it's from a student to a teacher.
That said, one should of course never use 貴様 (kisama) to an old lady you meet in the park.
The codes, the rules, are strict in Japan, but not nearly as strict as the West have them out to be.

Thanks a lot for sharing! I think it'll be very helpful to me.