Episode 3 is a nice bridge between EP 2 and EP 4 - it gives the game some new life, and the most dramatic chapter so far
Episode 3 continues everything I loved in Eps 1 & 2. It does have a couple of slow sections, but it also features some of the most dramatic and emotional moments so far in the game. It felt more linear (e.g. fewer choices with big immediate impact) than the other chapters -- but maybe we'll see the changes in coming episodes.
Length was good -- maybe a titch shorter than Ep2 (didn't time it, but around 4-5 hours is my guess), but I liked the progress of the story and the character development better in Ep3.
Keeping it spoiler free, you'll get some new (and very deep) wrinkles in the plot. The puzzles were very easy, and even the Quick Time Events were very simple and didn't require much 'twitch' (which I like).
Anyway, if you enjoyed Eps 1 & 2, you'll still be hooked!