1. Power consumption. Bram brought up a good point if we take Bitcoin to its ultimate extreme, that it will be people with access to nuclear energy (aka governments) that will take over mining bitcoin, since that is the cheapest route. This does not look like a decentralized future, exactly the opposite.

2. Proof of Time. There are attacks that can happen against purely storage based proofs. Bram's brilliant addition here is a proof of time to get around those problems. I can explain more if people want. NOTE: Filecoin's "Proof of Time and Space" has nothing to do with, nor is remotely related to, Bram's.

3. Decentralized Storage. Despite Bram's prolific work in decentralized storage systems, Chia has nothing to do with storing end user data (like Storj, Sia, Maidsafe, etc.). The data that is stored is junk, but that is okay (see below).

4. Storage waste. One of Bram's points is that this will start an arms race to build better harddrives. If people are successful at that, this will only make Chia better, and also make storage in general cheaper for everyone. So sure, maybe the proofs are wasting storage space, but it will make storage in general more economical.

Anything else I can answer in more detail?