I go back and forth on this. As someone who's taught English as a second language for many years, I can't help but alter the way that I speak. It does help a lot with people whose listening skills are weak.

But I sometimes think it does a disservice to students or people that I spend a lot of time with (like my wife, who's not a native English speaker). Yes, they understand me. But am I then making it harder to understand "real" English speakers who aren't as careful with their pronunciation?