You might lose a few from the txt spk generation, but aside from that I can't see it being much of an issue. On the plus side at least there's no variation between English and US English spellings unlike colour/color etc.
If you think it works for your branding, go for it.
I don't see any issue with the word "should", it's a basic common word in the English language. If a potential visitor can't spell the word "should" and you've got a paid product on your domain, you probably don't want that rubbish traffic anyway.