5) Speed: The WRT54G maxed out ~20Mbit (wired) and 6-12Mbit (wireless) running Tomato. The RT-N66U does around 50/225Mbit wireless/wired and the RT-AC68U pushes 400/900.
I get around 42Mbit routed throughput wired, with firewall enabled, QOS disabled running dd-wrt on a wrt54gl. Far more than your 20mbit, but still i think this is the keypoint where this device has aged too much.
Technology is dominated by those who manage what they do not understand.