I'm increasingly less concerned about the lack of replay protection because that issue has gotten a lot of press. I've seen lots of newbies asking about it, and I think services are very prepared this time around after the ETH/ETC debacle last year.
What I'm more concerned about is the increasing hash rate. Difficulty increased significantly on the last adjustment, and will likely do so again shortly before the fork. That means the hash rate will be split (between the two chains) right after difficulty increase. This could cause significant disruption, congestion and high fees.
Bitcoin Cash is rallying, and they are also set to fork to return to a Bitcoin-like difficulty algorithm a day or two before the Segwit2x fork. That's no coincidence. They are setting it up so users will go to Bitcoin Cash for the reliability and low fees, and hash power will come to Bitcoin Cash for the profitability amidst the difficulty clusterfuck in Bitcoin.
I'm hopeful, but I'm also keeping this disaster contingency in mind.