At this moment the DIR-655 reports a 72% signal strength from the SMC bridge in the same location as I attempted to use the DAP-1522. The bitrate of the connection is reported as 108. When I had the DAP-1522 up there, typical signal strengths were in the 70 to 80% range as well. When I reported >50% I was giving the minimum I saw. One obvious difference between the SMC unit and the DAP-1522 is that the SMC has 3 high gain external antennas, whereas the DAP-1522 has internals (not sure how many). The location in question is two 1.5 stories up and there are several sheetrock walls and a ceiling for the signal to penetrate in order to reach it. Still, the SMC manages to achieve decent high bitrate connections that the DAP-1522 can't (even in the presence of the nearby g-only network).
For what its worth, I also tried bringing the DAP-1522 into the same room with the DIR-655 and could not get any better connections than with it upstairs.
Back when firmware 1.2 first became available for the 655, I did try it, but it completely destroyed the signal strengths I could achieve (or, at least, the signal strengths that it was reporting). Typical drops were in the 30 to 40% range and whereas before the flash, I was able to get dual-channel connections, afterwards I could not. Lycan explained it was likely due to the "friendly neighbor" policy that the IEEE had added to the N spec. I live in a semi-rural area with a low density of nearby wireless networks (ok, yes, there are a few, but no more than that) so I would not have expected such a dramatic effect. Fortunately I was able to flash back to 1.11 and I vowed to stay there. There's have to be a VERY compelling reason for me to "upgrade", given the inability to revert.
All I want is a draft N bridge with a built-in gigabit switch that can get me better than wireless G connections. Is that too much to ask? It seems my choices at the moment are the SMC, which can achieve the connections, but does not have a gigabit switch and the DAP-1522 which has the gigabit switch but cannot achieve the connections.
Sigh.