I just finished the main story line. My verdict - LEGO Star Wars: The Complete Saga is a charming game. I'm charmed by it. Its only flaw (and this is only a flaw from the perspective of a 33-year-old man blogging about the game for no discernible earthly reason) is that it completely lacks depth.
There's a certain degree of twitch skill involved in conserving your collected coins, but aside from the blow to your pride that comes from losing them, there's no downside to dying, so all you really have to do is plug away and victory is virtually inevitable (there are a couple of puzzle rooms with infinitely respawning enemies that might stop you if you can't figure them out, but, again, for an adult, they're really easy to figure out).
In practical terms, what this means is that my brain is running at about 50% capacity while I'm playing this thing. That's not a bad thing, but much like with LEGO Marvel Superheroes, I'm going to want something more stimulating as a follow-up.
I think the most interesting thing about LEGO Star Wars: The Complete Saga is the way that some of its levels are basically toned-down versions of levels that appear in every Star Wars game. I've lost track of the number of times I've played the "snowspeeders on Hoth take down AT-AT walkers with tow cables" level (it was one desperate plan in one of the movies, but the games always treat it like standard operating procedure, and who even puts a tow cable on an aircraft anyway). Doing some cursory internet research (using this article as a reference), it looks like the answer is "six." Flying through the superstructure of the second Death Star, I've done at least three times. Pod racing on Tatooine, at least twice.
The non-vehicle levels were more unique. For obvious reason, they followed the same general plot as Star Wars games I've played in the past, but both LEGO Star Wars and just about every other Star Wars based action game have tended to pad their run times by including events that don't actually occur in the films (like, every Empire Strikes Back game I've ever played turns Luke's training on Dagobah into a full level, complete with invented swamp creatures, despite the fact that the training was implied to be very well supervised by Yoda himself). I suppose the reason the vehicle levels get repeated so much is because the vehicle scenes in the movies are directly convertible to video games. You don't have to invent new creatures to stage the Battle of Hoth, you just have to take that one scene where Luke takes down an AT-AT with a tow cable and repeat it a half-dozen times.