I also have a DIR-655, it's stable now but I was having problems after flashing to the 1.32na firmware and had to re-flash to fix it. A lot of people are complaining on the D-Link forums about the latest firmware being crap so if you go that route I wouldn't be in a big hurry to flash it. Mine is running great now and I have no complaints. I bought it for the Shareport feature that I use as print server for my laser printer.
Yep, never bothered upgrading the firmware on my DIR-655 past 1.2x something because it was just working. Except for the occasional power outage where I shut the UPS it was on down it's been up 24/7 through anything I've been able to throw at it for two years.
Edited to add: New netgear got nice reviews but apparently still has the old netgear problems streaming media.