I've heard different things about mineral oil. Some say its good for moisture retention/frizz control (sealing?) and others say it builds up as if you're putting Vaseline in your hair. Thoughts? A curl cream I want to try has it.

It's this one:
Amika Obliphica Curl Defining Cream - NaturallyCurly.com

Ingredients:
Aqua (Water), Mineral oil, Petrolatum, Cetearyl alcohol, Stearic acid, Cetyl alcohol, Phenoxyethanol, Hippophae rhamnoides (Obliphica) oil, Argania spinosa kernel oil, Polyquaterniu-7, Cetrimonium chloride, Triethanolamine, Fragrance, Panthenol, Sunset yellow
2A/B. Mix of fine, medium, and coarse (mostly medium). Dense. Mix of normal and high porosity.
Dry climate.