I've been a big fan of all the Lego games, so my son & I were excited to pick up this one when it first came out. After playing it to about 85% completion, I have to say that overall this one is a pretty big letdown.
The format of the previous games has been pretty much the same - there's an overall hub that serves as the central area for the game. From there, levels are grouped together by story (about 5-6 levels for each movie/storyline). Each level contains a variety of hidden areas and secrets that can be accessed as the player opens new characters in the game, adding to the level's replay value.
That philosophy seems to have been rethought for this game, and not for the better. Instead of one hub, there are 6 - one for each of the 1st three movies, and three for Crystal Skull. The hub is a giant area where you can locate new characters and vehicles, and access the story and bonus levels. The hubs are fairly involved, and are set up the same way the levels were in the previous games (obtaining a new character lets you use their new ability to access a new part of the hub). The hubs are pretty well designed. My one complaint is that almost every new character remains in the area where you first purchased them, so remembering where to find the one you need can be difficult. Also, some of them are in very far-flung locations, so it can literally take about 5 minutes of just walking/driving the entire way across the hub to find the character with a wrench (for example), and then going all the way back across the hub to the entrance of the level that you need him for. I don't know who came up with that, but it's a TERRIBLE idea and a boring chore.
The levels themselves have been simplified WAY down. There are no secrets, there are no hidden areas, there is no reason to play any of them through more than once. Only the most rudimentary thought seems to have gone into each one. Gameplay is still the same as it ever was, and it's enjoyable, but the level design leaves a LOT to be desired. Generally, an entire bonus level will consist of one puzzle - for example, use the shovel to dig up a spear, throw the spear into the hole and use it to climb up to a ledge. Hit a switch with the whip and you're done!
The story levels too are much shorter than the levels in previous games. As an example, anyone who has played the first Lego Indiana Jones game will probably remember the mountain level from Raiders of the Lost Ark. That level begins in Marion's bar where you have to defeat a boss while the bar burns down, then moves into the mountain passes, then to a mountain temple, and finally to an army outpost. The equivalent level in this newest installment has players beating a boss in Marion's bar and THAT'S IT! That is the whole level. Each story level can be completed in roughly 5 minutes, and has no replay value at all - no secret areas to discover or any reason to come back to it again.
My final issue with this game is that it freezes on a fairly consistent basis - we've had it lock up about 15 times now, in all different areas, though the Raiders hub tends to get it the most. From poking around on forums, this seems to be a fairly common complaint.
If you're a fan of the Lego games, it's worth playing this one - it's still fun, even if it is a bit lacking in comparison to previous ones. However, I am keeping my fingers crossed that they do not retain this format for the Lego Harry Potter game coming out next year.