MAMEUI64 seems to no longer honor the mameui.ini values for current_software_tab and default_system. It changes them to whatever it was left on when it exits, but when you bring MAMEUI back up, the caret is not moved to the last rom used, and the software tab is back to "SW Files" if it was left on softlist. Media Files returns to the tab on restart.
current_tab appears to work fine.
There's something funky going on with the softlist (SW Items) tab on my system.
I hope that's the last thing I notice about 0.189.