I upgraded my G300NH to the newer 19484 build earlier this week. While it resolved some of the poor wifi issues, it introduced some weird behavior. First being , my wife's Atheros based wifi card stopped getting authenticated to the router (worked fine on the older build). I dug around and discovered the "wireless' mode is broken in the new build. Since I had the setting set to 'N Only', it caused the Atherors based wifi cards not to get authenticated. I changed the mode to "NGMixed" and it connected fine.
Signal was good, especially for 3 of my laptops downstairs in the house. But everytime I'd turn on my Xbox and start playing BLOPS2 online, the router will hiccup momentarily and drop all connections...even wired (I'd get kicked out of Xbox Live). With no intervention, the router would fix itself in 20 secs or so and everything is connected again.
Then I found another yet newer build from the DD-WRT community (not Buffalo). Flashed that yesterday morning and so far, ALL my issues have been resolved. Haven't rebooted the router since yesterday. Have gamed on Xbox last night with 2 hours (while my wife was surfing on my laptop, kids streaming Netflix on Wii U)....zero issues so far.
Ironically that the 'best' firmware that worked for me is from the great DD-WRT community and not Buffalo.
If I have any issues with this firmware, I'm throwing the Buffalo router out the window and going to Linksys (my older routers were all Linksys and I had the need to tweak them..they just worked).