No problem on landscape. Haven't had a chance to run any group instances. Much smoother than before, and graphics running at much higher level than before with minimal FPS loss. Currently running Very High at 40-60 FPS with occasional drops (and spikes indoors over 100 FPS). I don't have a high end system. ASUS Laptop, Intel I7-7500U @2.7GHz, 12GB DRAM, NVIDIA 940MX and a slow-as-molasses 5400RPM 2TB HDD.
I do get crashes, but they aren't while playing. I often crash when exiting game, or logging off characters. Also, I can't use the launcher by keeping it open, as I used to in 32-bit mode. A successful exit (unusual) with Launcher open and the Launcher never acknowledges that the game has exited - it keeps saying it's running. I am on several servers, so I prefer to keep it open so I don't have to restart launcher, precache, then enter my gosh-awfully long cryptic password just to change servers
I'm reluctant to go back to 32-bit mode, but I may have to. Being able to see Middle Earth in Very High Graphics and see how beautiful it is makes me sad if I have to lose that to able able to switch between characters and servers. Hoping they can patch this soon.
I have CCMSS (Character Creation on Many Servers Syndrome). There is no Cure. Over 80 characters on 12 Servers: Gladden, Firefoot, Landroval, Crickhollow, Riddermark, Silverlode, Arkenstone, Brandywine, Withywindle, Laurelin, Evernight and Eldar before Exodus; after the Diaspora, on all English Servers.