1. No obvious setup instructions are available anymore in the installation wizard's last step (if there were problems with writing to file zabbix.conf.php) as the button Retry is removed and the instruction thats there doesn't look finalized comparing to 2.4 version of Zabbix setup step page.
Please see side-by-side screens.
2. Also very neat Test button for DB connection is not there anymore that can be considered as a step back, if there are no other considerations about it.