As a player who was a Cata baby, I was very curious about classic, especially since I never saw the world pre-Cata. What I found:
I have been lost in the Barrens for 5 days now and have only been able to complete 6 quests. However, while sometimes it was frustrating because I didn't seem to make much progress, I had a lot of fun seeing the Barrens as it was.
I enjoyed the challenge of figuring out my class/spec, even though I screwed it up. I made a druid, thinking I could stealth around as a feral. Oops, feral is more of a tank, so I switched to balanced... Oops, I put all the talent points in feral and there isn't a druid trainer in the Barrens. This is probably why I struggled killing stuff as balanced.
The best part about playing the demo were the people I have met in the Barrens. All were helpful and all included me in killing the big bosses around the zone.
A friend told me that this is what most people miss about vanilla - people helping and including people, making it a friendly community. I hope this aspect stays when the game is released as it made being lost in the Barrens fun.
Hopefully before the demo ends, I'll find that Stolen Silver that I spent an hour looking for last night. ;)