IOTA allows to create static web content on a decentralized platform. The advantage is that the content is free to host (besides a minimal amount of proof-of-work) and protected from DDOS since that would require to DDOS every single full node in the network.
With the addition of Qubic, it will be possible to create dynamic websites which can react to outside changes such as real world data fed into the tangle through oracles or user inputs in form of transactions that the user attaches to the tangle.
In most cases, it is still much more efficient (regarding costs, convenience and latency) to buy a centralized webserver, therefore it is not a sufficient replacement for these. However, a decentralized dynamic website would open entirely new use cases for trusted content.
It is "trusted" because the underlying code is stored publicly on the ledger which makes the working of the website pretty much transparent. In addition to that. A sufficiently large q-node assembly will ensure that the code is indeed executed correctly, making the website secure and reliable.
For decentralized computations don't the oracles change prices based on consensus from the nodes running said computation? If so aren't they forced into being competitive to a web server with enough demand? As far as price is concerned. Sorry, this is most likely a post-Q release question but if the cost is really high there are much more limited use cases here. Latency is only a trade-off for the time being until the network scales. Should be lightning eventually.