Oh man... I want a cuben tarp. Hard to justify buying one when I already have a silnylon tarp that refuses to die.
I think it would be helpful to compare the CubicTwinn with the MLD Grace Duo and BPL Stealth Nano. Here are some quick numbers from their websites:
Dimensions (ridgeline, front width, rear width)
CubicTwinn: 117", 110", 83"
Grace Duo: 111.6", 108", 93.6"
Stealth Nano: 108", 102", 68"
CubicTwinn: 5.5 oz
Grace Duo: 7.7 oz
Stealth Nano: 4.95 oz
Grace Duo: $275
Stealth Nano: $330
MLD and BPL claim no need for seam sealing, GG... I don't see anything about that yet (I'm in a bit of a hurry, so maybe I just missed it).
The dimensions are all reasonably close between the three. Looks like the deciding factor would be price (MLD the winner), weight (BPL the winner, but not by much over GG), and how much you want to seal the seams.