I'm not sure about that. If the main matrix server disappeared today that'd be problematic. Yes, you'd have history locally but the same can be said for any native client that stores history locally.
As far as I know there is no way to migrate matrix history now. Is there? (genuinely curious)
for everything else we’re working on decentralised accounts via MSC1228.
there are also migration scripts and tools to move you between accounts on different servers today (like email).
This ^^ Currently a large amount of users (I'm told around a half, but I'm not sure) have matrix.org as their home server. So Matrix is effectively building a power-law network with all its drawbacks: when the "power node" of the network goes down the whole network falls apart.
After Synapse 1.0 is released (sometimes next month, IIRC), I'm definitely deploying my own homeserver, and federating it with the rest of the world.
I guess this is the real problem for me - i would love to federate but i can't possibly police or enforce what servers/channels are small enough that my users can join them.