I have a hard time pinning down my thoughts on Moby Dick. The vast number of exhalations on whaling do vary drastically in regard to my interest level. I do think that ultimately the reader's experience with Moby Dick will ultimately come down to their reading endurance, and general interest in the ideas of the novel. Still, there are many aspects of Moby Dick that you would be hard-pressed to refrain from praising.

Characters
The characters in Moby Dick are incredible. They are well distinguished from each other, and Melville dedicates a lot of thought to the motivations of the characters. Moreover, the interpersonal relationships of the characters are also captivating in that they are shared between great characters. While I feel that the latter half of the novel broadens its scope outside of the individual for the most part, it makes up for this broadened scope with the "Gam" chapters that see our beloved characters meet other whaling ships.

Moments of tension
I could name a few instances where Melville cleverly builds to a climactic moment. These instances generally surround Moby Dick, and they are well executed.

(Maybe)
Spontaneous banger lines. Just sudden gems from Melville thrown out randomly. They can be easily missed by the careless reader, and I think these make up most of Moby Dick's brilliance.