Oh, I would never notice minor hair changes, either. I didn't actually notice Jack's haircut in the ep, either! On the other hand, there is this great bit of dialogue from the show, when Jack visits Daniel in the infirmary:

"Did you get your hair cut?"

"Yeah, why?"

"No reason."

And, of course, the delightful echo of this in Fallen, after Janet gives Daniel back his glasses:

"Do you recognize me now?"

"...Has your hair always been that way?"

"What way?

"Never mind."

What can I say? I love these two. :)