Use the AC66U Router and my printer and fast and instantaneous in print with official Firmware from ASUS now when I update to Firmware from ASUS Merlin the printer is extremely slow and each print takes approximately 2 minutes or more after the command.
Which firmware specifically? What printer? How is it connected? What client computer is it slow from and does using another computer help?
Additionally, was a full reset to factory defaults performed after flashing the latest firmware? And, in addition, was the router configured manually and minimally to secure it and connect to your ISP (without using a backup config file)?
To answer your post at face value with the few details you've provided, I would say it's 'just you'. I have not heard of anyone else having this issue.