I'm a language geek, but I try not to be a nit about it. I like the subtle nuances in choosing the "right" word for a situation, but not at the expense of connecting and communicating with real human beings. However, sometimes a small change in word choice can have a large impact on clarity.
In JP's Nothin' But .NET class last week, we had an object called "criteria." (He was creating a DSL for generating SQL statements. Neat stuff.) My brain kept tripping over the example, until I realized, "Oh! Your criteria is a single thing, and I'm expecting it to be a collection. Ah ha!" So I suggested a name-change to "criterion," not to be pedantic (I swear), but just to improve clarity.
A little time passed, and then a student raised the objection I was expecting. "Well, actually, Merriam-Webster's says..." I know this objection well; I've explored it, and I've read Merriam-Webster's editorial philosophy (Did you know your dictionary has an Introduction?). M-W has a descriptive focus, not prescriptive; their intent is to capture and document language usage in the wild. It's a good resource, but not when you want to know the "proper" use of a word.
Knowing this did not improve my image in the class.
Ah, well, I gotta be me. Teasing me, one student said, "Hey, you know so much about dictionaries. Do you have strong opinions on hash tables?" No... that's my dad!