I just bought the TL-WA1201 access point, and had difficulty with the Multi-SSID setup (80% packet loss when using any SSID on a VLAN).. A quick search in the forums, and I saw the advice to upgrade to the Beta firmware to resolve this issue.
So I upgraded from 200709 to 210104, which resolved the packet loss issue.
Now, the current issue is that ALL clients connecting to this AP, are getting speeds of 11g in 2.5GHz, and 11a in 5GHz.. i.e 54Mbps
I tried to hardcode the mode to n on the 2.4GHz, and to ac on the 5GHz, but no joy. Channel width and number changes make no difference either.
I'm not sure whether this was impacting the previous non-beta firmware or not... but downgrading is not an option since it destroys the Multi-SSID functionality