Like all 3e published modules there's a lot of filler encounters. Fights that exist solely to get people to the requisite level. Well, that's a problem with 3e-5e really. With fewer encounters/level in 5e you could certainly jettison a few of the weaker encounters.
I ran the middle chapter for Living Greyhawk and found it... adequate. But it was one of the less interesting chapters. But it was still interesting and I'm curious enough to consider running it again in the future.
I don't agree that it has a lot of filler encounters, (or more precise, that they felt like fillers while running the module). I think the encounters felt quite natural. Some encounters were a bit too easy, but that was mostly due to it being a bit sandboxy. Should work better in 5e than in 3e though.
EDIT as Jester Canuck noted, in a later post, he felt that many encounters in the last dungeon was filler material, something I concur with, as my following comment notes:
I didn't like the finale of the module and never ran it. I think some alternate ending would be much more interesting.
[sblock]The ending is a big dungeon where you end up fighting a avatar of Tiamat. I really don't like dungeons and it just felt anti-climactic after the super-cool battle in the city. I chose to just end the module after the big city fight, without ever fighting the avatar[/sblock]
I would give the module 5/5. The story really works, the encounters are cool and it's not a dungeon crawl (for the most part)! It's also easy to run and doesn't feel like a railroad. If the players go outside the assumed scope of the adventure I think it would be relatively easy to modify it to reflect the PC's actions. It also has some sidebars talking about some assumed out-of-scope PC actions, which I think is really cool.