IMO the argument that we are making society stupider by introducing spell check is nothing more than anecdotal evidence and conjecture.
Actually, I'm a much better speller now because of spell checks than I was in school, so this theory is incorrect. I learned over time how to get rid of the little red lines.
Auto-correct on the other hand is pure evil.
I'm certainly all for a spell checker in mIRC. I'll have to check out some of these scripts.