All I can say is IF you upgrade firmware on your DIR-655, my only advice is to ONLY up it to firmware 1.21 WITHOUT shareport.
I have a DIR-655 HW: A1/A2 FW:1.21
and the ONLY problem I experience sometimes is slowness on wireless N like every 5-7 days.
Since I am the only one in the house who uses the wireless all the time, I just login (put a ADMIN password on your router and be sure to DISABLE remote ADMIN for your own security) and goto Tools/System/Reboot and the router reboots, and speed is back up kickin' it.
This is just a little thing to do, and I can live with it.
I just would NEVER upgrade past 1.21 because it will, correction CAN, brick your router.
And then you have a nice paper weight.