So, I just flashed the FW BACK to version 3.10 on my Rev C and the "N" speeds came back immediately. I'm now back to 243-300mb/s and fairly unimpressed with the latest FW revision. While it gets rid of the incredibly annoying CAPTCHA obligation and bypasses the 30 second "please wait" screen, it clearly lost alot of functionality somewhere along the line. The Intel 5100 is relatively common these days and for it operate at only 5.55% of it's capability following a FW upgrade is insane. If I were an end user this thing would be RMA'd tomorrow. This is embarrassing for both D-Link, as well as all resellers of your product and creates higher expense for the reseller in tracking, requesting the rma, then shipping for both parties.
The sad thing in this giant mess is that I decided to see if this thing (which, on paper is about the best value known to man given the amount of RAM, 400Mhz NPU, and flash rom) is compatible with DD-WRT and the crazy thing is that it actually IS... kinda... not really. See, unless you're willing to take the time to build your own JTAG cable, you can't do jack with it.
Why not just separate yourselves from the pack by putting together the best enthusiast router known to man by preloading it with ridiculous FW? We won't tell anyone and even if we did, they'd probably buy a Linksys from the kid at Best Buy anyway so hook it up please.