It's not bad and you're given the option to just upgrade the SALGW component and not use ADS if you have no need for it.
Though, there are a few issues with the old SAL where it was more permissive about certain things - like having IPs with a space at the end if someone copied it wrong from Excel. That will make it not start after you upgrade.
And, it always looks for a GUI to install if you do it from putty, so unless you have access to a console/VNC, you'd have to do the install unattended and fill out the .properties file.