Have you ever been working on a paper at the last minute, say the night before a conference, and found yourself with rather limited time for proofreading? Situations like that happen, and even if you prefer not to use a spellchecker, it's a tool that could be allowing you to do a better job when you don't have the time to be as meticulous as you'd like to be. I'd never blindly rely on one, but they can certainly help speed up the process.

The thing that seems to set people off is the fact that spelling and grammar checkers make mistakes, but maybe it would help if you tried to think of it differently. The spell checker isn't telling your where the spelling errors are, but where they're more likely to be. Think of it as a purely statistical result.

Now, as you're proofreading, you're searching through the text for errors. The result of the spelling/grammar check tells you where the probability for errors is the highest. What makes the most sense, a blind uniform search or one where you spend a little more time where you know errors are most likely?