Hi subcommitteez,
Welcome to the Mattress Forum! 
They have been brought up here on the forum before. See post #104 here.
From that post:
They have two different comfort offerings (from information provided to site member Ari by Tomorrow Sleep).
Medium firm
1" 3.5lb Memory Foam Layer
1/2" 2.5lb Air Cooled Comfort foam layer with Gel (not sure if this is memory foam or poly foam)
1.5" Dynamic Response Foam Layer (density was not provided – this is probably polyfoam)
6" coils at the bottom for additional support."
Medium soft
1" 4.8 lb Viscoelastic (memory foam)
2" 2.5 lb foam layer with Gel (not sure if this is polyfoam or memory foam)
6" Series coil
6" x 3" Foam rails with Side Ventilation
1" thin base foam layer which the coils rest upon
Tomorrow Sleep is a managed independent of Serta Simmons Bedding (SSB) by Bryan Murphy, a successful eCommerce/Software entrepreneur (WHI Solutions). SSB is building their hybrid mattresses for them (see this article).
The Medium Firm uses a total of 3" of comfort materials, with the memory foam being a bit lower than what I would normally recommend (3.5 lb vs. 4 lb), and they didn’t provide the density of the “Dynamic Response Foam Layer”. The Medium Soft uses a higher density memory foam, and the polyfoam layer beneath that uses a better density of foam. There isn’t more detailed information on the spring unit listed on their web site.
They unfortunately don’t provide detailed information about each mattress configuration on their web site, and I would advise caution against purchasing anything before knowing of all of the componentry on the inside of the product.
Phoenix