Who does tons of side quests their first playthrough anyway? The first time I play I usually just rush to finish the story, then I'll go back again and do all the things I missed the first time.
Honestly, I think XIII is going to be XII all over again. Everyone hates it, 10 years later, everyone loves it. I really liked the character development in XIII. It had a lot more depth and reality than other games. The characters were actually relatable. It wasn't a cliche random guy with big sword saves the world game. Square Enix is known to experiment a lot. Granted, this wasn't their best "experiment" but it wasn't dreadful. The gameplay was actually pretty fun. I didn't really mind the hallways, because no matter what people say, X was a hallway with towns. >.>
I DID miss shopping in towns as a little break in between, but it wasn't that big of an issue. If you think about it, towns wouldn't have really fit into the story here. The characters were l'Cie running for their lives.
I also grew to like the difficulty. It wasn't too hard, but wasn't a pushover either. XIII-2 was way too easy. I rarely ever had to paradigm shift, and the battles got really boring and repetative. In XIII, you had to know what you were doing or you got screwed. It was a nice change of pace from the easy games these days.
the only thing XIII could've done better IMO was letting you choose the lead character as early as you got a second party member, and being able to choose everyone's starting class, second class, and third class before they were all available. That way you could make a combo of whatever you wanted/needed.