As someone who enjoyed 13 and 13-2, I was undoubtedly excited for LR but now that I've played it for around 4 hours, it has become one of most annoying RPGs I've ever played. The series took a turn from being linear to non-linear but the problem with LR is that it is too non-linear. The game employs a time/day situation similar to Majora's mask (i.e. the clock is constantly turning). Sometimes the game makes you wait a whole day before the main story can progress and in that time, all you will be thinking about is 'what do I do now' as you are already told that you have only a maximum of 13 days (if you do enough side missions). At this point, you become focused on completing side quests so that your 'day' doesn't feel wasted. Well I can say one thing though, the whole day IRL felt like a waste to me by playing this.
The whole concept feels stressful for an RPG. The game also has no levelling system and purely focuses on the costumes that Lightning wears. In addition to that, you don't automatically get moves like Guard or even Attack with the different costumes. To get these moves, you have to fight countless enemies and just hope that your luck pays off. Seriously, the moves Fire and Blizzard are rare enemy drops. You do however have these points called 'Eridiam points'(EP) which you can use to stop time for a while or to buy items but the problem with that is that it can take a very long time to replenish EPs (usually through battling).
If I was to honestly give Lightning Returns a score out of 10, it would be a 6 (and that's being generous). [Edit: This is subject to change as I progress through the game]
tl;dr: Based on first impressions, don't bother with the game! The time mechanic makes it feel like a chore rather than a game. I'll write a full review after finishing the game.
Edit: I'll be playing through to completion and will be working towards getting a platinum as I am a completionist. I'll create a review thread then detailing what I felt about the game overall. I hope it grows on me...