I think the lack of "replay protection" is what scares me. Replay protection lack means that, theoretically, if you made a transaction on one chain (e.g. the Bitcoin Core chain), a node on the other chain can replay your transaction (e.g. the Segwit2x chain).

For example, if I sent Bob 2 BTC on the Core chain, Bob can replay my transaction on the 2X chain, also sending him 2 Segwit2x Bitcoins. If they don't fix that soon, that could end up being a large problem.