well, let me give what I think is a good example of the difference between 2E and 3E... our last big 2E campaign was set in Kalamar (yes, we had the old version from Kenzer)... It was a terrific campaign that lasted about a year where the party ended up saving the world from eternal darkness. The group's halfing thief was the highest level at the end of the campaign at 10th level with the big award for ending the campaign/saving the world at the end. My human ranger ended up at 9th, and the elven fighter/mage was like 8/9 (gotta love those 2E XP progressions!!)
We recently finished a 15 month long 3E campaign, also set in Kalamar. Most of the group ended up just getting into Epic Levels, with the highest party member being the human fighter/ranger at 23rd, I believe.
So, it is quite different, and the guys never got bored with their PCs in the teen levels. (I was out of action for the beginning of the campaign due to work commitments, so my PC came in at a high level.)