Time for a horn toot... When in 6th grade I won the Kitsap County Spelling Bee. Gramatically, I'm OK but not as good as real scholars. I have always looked at spelling though and Word docs or e-mails that go to customers with a bunch of words mis-spelled have got to leave some kind of negative impression.
My old business partner never finished any school above 9th grade. While he was definitely a personable guy with good sales and relations skills his spelling was atrocious. If he wrote something for marketing materials I would have to completely redo it. Proposals and especially e-mails were hardly ever able to be checked though. After doing reconnaissance through old e-mails for viable customers, I saw a lot of the e-mails that went out and they left me with the impression that I was back home in Seabeck, Washington... home to a lot of kids that grew up in logger families and basically dropped out as early as 7th grade. As a client, I would take notice of this and I'm sure it had an effect on us, especially toward the end of my partner's reign where his attention to detail was next to nil.
That said, there are definitely mis-spellings in my own posts and they are not related to a lack of the ability to spell the word but to my hunt and peck typing skills...which really suck!