The neo-air story is getting a bit confusing; I only have experience with the initial/standard yellow neo-air. Now there's the trekker and the all season models.

In size "regular" (72" x 20"), the standard weighs 14 oz with a listed R-value of 2.5, the trekker weighs 20 oz with R-value listed at 2.0, and the all season weighs 19 oz with R-value listed at 4.9.

So the Trekker is meant to be more durable, but dispenses with the reflecting layer so actually has a lower R-value than the lighter standard model. The all season beefs up the R-value, but again, is heavier (by 5 oz in size regular).

To make things even more confusing, now the XLite is coming out, yet another neoair model. 12 oz in size regular, and R-value increased to 3.2. Looking at the manufacturer's website, I get the sense that the original model will no longer be made (?). Not sure.

In any event, the difference in size regular between the coming XLite model and the All Season is a whopping 7 oz. A 1/8" thinlight ccf pad, in contrast, weighs 2.2 oz, and would add a bit to the 3.2 R-value of the XLite.

Guess which I would rather carry? Of course on summer trips a person could dispense with the thinlight pad as well.