I dont think there was anything new in this that I hadnt seen before in discussions of PoW vs PoS.
The main point against PoS was that unlike in PoW, anyone who is new to the network or goes offline and then is reconnected is required to trust some entity / community / etc, that the blockchain they are using is the 'correct' one, and not one which was reforged over a period of time using old private keys purchased from former holders, etc.
"This is not a distributed consensus! It is a different sort of consensus, which may be formed amongst always-online peers in a decentralized way, but depends on trust for new users and temporarily offline ones. It is correspondingly vulnurable to legal pressure, attacks on “trusted” entities, and network".
We already understand that there is a human element to our consensus algorithm, DPoS. You need to trust the majority of the delegates. You need to trust the developer/website/community that you are downloading the snapshot from.
So it is true that this is not as decentralized, and requires more trust, than an idealized proof of work system, such as the one that bitcoin had before mining pools.
However, mining pools are also a central point of trust, you have to trust that the top several mining pools wont collude to screw you over in bitcoin, just like you have to trust that the delegates and the dev team and the bitshares community are not colluding to screw you over by giving you a false history of the bitshares blockchain which was reforged from old private keys or false delegates or something.
As bytemaster posted in his blogpost about this, part of our solution to the problem is snapshots. Every 101 bitshares blocks is considered a snapshot, which solves the nothing at stake problem for old private keys that are more than 18 minutes old. (And there is no way you can unload a big position without massive slippage in 18 minutes). This does mean that you need to have some trust in the delegates, dev team, etc. If you have no trust for these entities and think they might be scamming you with a false blockchain history, you shouldnt use bitshares. If governments put massive pressure on all delegates and the developers, and try to force them to give people a false history of the bitshares blockchain, then you should be wary of trusting bitshares.
In more normal situations, the tradeoff is a probably good one because we dont pay the huge cost of PoW. But of course, DPoS is still experimental, way more experimental than PoW is.