It shouldn't affect the ordinary user experience at all. Basically we have given developers the ability to be much more specific about what information they pull from the Steem blockchain. Until the changes go through, some developers don't pull any specific information from the blockchain, they just basically take a whole bunch of data and then only use the data they need. But this is a very inefficient process that has contributed to the size of nodes with no real benefit. So we're making extra sure that all developers still have the ability to pull whatever information they need from the blockchain–so their apps don't suffer–while getting rid of the ability to pull so much data all at once for no good reason.

The only meaningful change is that this will help reduce the size and cost of running Steem nodes, which will make it easier for anyone to run their own node, theoretically leading to increased decentralization.