The importance of being Earnest

Okok..actually I wanna say the importance of spelling, and I couldn't think of anything smart to put as the title, while using that phrase. (The Importance of Being Earnest is actually a play written by Oscar Wilde) hahaha. Haven't read the play OR watched the movie, but it must be good. Oscar Wilde mah. He's got wit! hehehe. Anyway my point is, spelling is IMPORTANT! It IS! You might think "aiya, one alphabet only wrong ma". but NO! For example 'than' and 'then':

"I wanted to go shopping and than I forgot."

Okay, maybe it's a bad example but you get the point. It annoys me everytime I see errors like that. If you misspell a big word like 'Supercalifragilisticexpialidocious' then its okay lar...(don't worry, googled it and checked with Wikipedia :D) But then again, its not a biggie. It won't cause the end of the world. I only have to re-read the sentences two or three times just to make sure I get the correct meaning.

So.....is spelling that important?