I think Worf has probably the best character development over the 7 seasons of anyone. He is definitely different, but I think it's a gradual enough change that it doesn't seem forced. If you see S7 and then immediately watch a S1 ep, then it will be jarring.
I actually think his move to DS9 was a few steps back from where he'd gotten on TNG. To me, TNG S7 Worf and DS9 S4 Worf are veru different. He goes back to being all grumpy and "Klingons do not..." and reminds me more of TNG S3-4 Worf. Maybe it's because he's in a new place and Worf is not one to get comfortable with people easily. He starts to settle in right about the time his wife dies (Worf just cannot catch a break with the ladies, can he?)
I don't think they really got his "look" right until the 7th season either, when he finally got rid of the ridiculous pageboy hair and got the ponytail.
I agree, though the long hair was about halfway through season 6.