OK, so I just saw a tent people loved by Hyperlite, made of cuben and pricey. It looks fantastic (it should -- costs around $700). My question is: are there any negatives to cuben? The positives are obvious, but some of us are on somewhat of a budget...<grin>

Negatives:

1) cost
2) cost
3) it can develop pinhole leaks as it wears (folding, flexing, crumpling)
4) it lets in light (not easy to sleep in)
5) it can be loud (kind of crinkly)

Cost, cost, cost (one more vote for cost than BZH)
Less privacy because it's more than translucent, perhaps a cross between that and transparent
I really haven't noticed the noise issue, probably because my head is surrounded by the sleeping bag hood.
I am concerned about the wear issue, but no basis yet for comparison

I still haven't used my cuben fiber tent enough to determine if it is more subject to wear and tear. That's because the last few years I've mostly been backpacking with family members, using my Tarptent Squall 2.

The weight difference between a cuben tent (mine is 17 oz. with guylines and stakes) and a lightweight silnylon tent such as the Tarptent Protrail (26 oz. with guylines and stakes) is not that great and may not justify the extra cost per ounce of weight saved. Only you (and your wallet) can decide!