If you got 1.21 then don't upgrade.
I got 1.21 on a A1/A2 DIR-655 and I will not change it for anything.
I got
Apple TV2
Google TV Sony Blue-ray STB
Macbook Pro
Macbook
17" iMac
Dell Inspirion Laptop (old)
and a Wii
all doing wireless
plus a Dell PC (old/2007) and 21.5 iMac and a Kodak ESP6150 printer, Dlink NAS DNS-323, Sony S460 Blue-ray all wired into it (using a gigabyte 4 port switch also off of one port) and I NEVER have any problems.
I have had the same setup on my router for I guess about 3 years or more.
It does not fail, don't have problems .
Pick channel 6 or 11 and uncheck Auto roam channels, for me I get a great signal (everything is 80% or better on 802.11N).
Here in Miami,FL in a townhouse, I search for networks and I got like 7 wireless AT&T u-Verse ones around plus 5 others.
So I get a lot of problems if I let it automatically search for a channel because just about everyone is on channel 1. Just set a channel high up and forget about it.
The only thing is my daughters DSlite will not connect because I use WEP security. The Sony PSP will connect but for the DS I would have to lower or remove the security.
Just never upgrade the firmware.......
"If it ain't broke.........don't fix it"
Just do not upgrade the firmware.......not worth it.