Well, anyone who's ever come to the SG chat on AOL, knows I am a major Daniel fan. For all that, I was torn about the haircut thing.
I think my favorite look was from the very first few eps which is longish but not near as long as it was in season 2. At first, I was none too fond of the short hair but it's grown on me (pardon the pun)in season 4. I think it's because of the longer sideburns.
Hair aside, I really like the Daniel of season 4. It's like he's come through the dark times and has survived. Now, he's more confident in his abilities and in his place on the team. Gone is the geek but the boyish charm and enthusiasm has remained. God bless continuity and a show that let's its characters grow into themselves!