seriously... nubits is a joke... to depend on fiat is exactly that, what cryptocoins want to avoid. so its fiat. you can keep usd as well...
NuBits is a quite successful joke so far.
Compared to USD you can transfer NuBits to your wallet¹ with short transaction times and the entity that issues this currency is not the FED but a decentralized autonomous corporation owned by the NuShares holders.
¹ plus you can easily transfer NBT to other exchanges (in difference to fiat) - admittedly there's only a few exchanges that have NBT listed so far... but hey, NBT is only roughly 2 weeks on the market!