Without any experience with the inner workings of the firmware, I would hope that the existing 5GHz driver be retained and maybe Asus update only the 2.4 GHz driver.
I think I will be going with Merlin's 270.26b for now.
I agree that the 2.4GHz. signal using 270.26b is at least slightly stronger than the 354 firmware one (5 bars for 270.26b., 4 for .354 in my living room, at the other end of my house). The 5GHz. signal seems about the same. This is just from signal strength, though, not from testing throughput, which can have different results. So I'm not currently motivated to move to .354 firmware, and will stay with 270.26b.
However, in respect to functionality compared to other routers, the RT-N66U is head and shoulders above other routers that I've had. Both the user interface (web GUI) and routing/wireless functionality have been good, and continual improvements are made. Yes, there have been problems, but that's not unusual, what's unusual is that both Asus and RMerlin have continued to work on the firmware for this router, and to put out timely fixes to problems. When I see slightly lower wireless signal strength, I'm still seeing better than I've had before. If I try new firmware and there are problems, there's always a stable version that I can fall back to that basically works well, at least that's been the case for a long time now.
With Linksys, Netgear, and DLink, I had problems that I'd wait 3-months for a fix for, and generally the fix would break other things, occasionally they'd fix a problem. Or a fix would never come, they would just stop supporting the "older" routers. It was more a process of learning to live with problems than expecting fixes. I'm very happy with the high level of functionality that this router has provided, and the fact when new features are introduced that have problems or problems crop up, I can expect them to be fixed in the near future.
