Never noticed this before, but finally annoyed me enough to start some diagnostics.
Laptop: Late 2011 17" MBP (Dual band wireless-N, confirmed all works fine)
Router: WNDR3700v2 running 1.6.1
Settings: Access Point / Dual-Band / 40Mhz on 2.4G / 5.0G, channel 9, 2nd channel below / channel 153, second channel below.
I'm the only 5.0G network, and the only one on channel 8-9 (others around me are on 6 or 11).
5.0G from ~18" away connects @ 270Mbps transmit rate, 2.4G connects @ 130Mbps, maximum.
Ideas? Seems this should be connecting at *much* faster rates.