I have an MR33 at home and using Speedtest.net on my 75/20 Mbps line, I get 72 Mbps download and 17 upload.
If I do an iPerf TCP test between my Macbook Pro and my Windows machine (On the LAN) I get this:
Connecting to host 172.20.Y.Y, port 5201
[ 4] local 172.20.X.X port 60762 connected to 172.20.Y.Y port 5201
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-1.00 sec 36.6 MBytes 307 Mbits/sec
[ 4] 1.00-2.00 sec 36.8 MBytes 309 Mbits/sec
[ 4] 2.00-3.00 sec 34.4 MBytes 289 Mbits/sec
[ 4] 3.00-4.00 sec 32.3 MBytes 271 Mbits/sec
[ 4] 4.00-5.00 sec 31.0 MBytes 260 Mbits/sec
[ 4] 5.00-6.00 sec 33.9 MBytes 285 Mbits/sec
[ 4] 6.00-7.00 sec 34.7 MBytes 291 Mbits/sec
[ 4] 7.00-8.00 sec 32.9 MBytes 276 Mbits/sec
[ 4] 8.00-9.00 sec 31.1 MBytes 261 Mbits/sec
[ 4] 9.00-10.00 sec 34.8 MBytes 292 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth
[ 4] 0.00-10.00 sec 338 MBytes 284 Mbits/sec sender
[ 4] 0.00-10.00 sec 338 MBytes 284 Mbits/sec receiver
Accepted connection from 172.20.Y.Y, port 51240
[ 5] local 172.20.X.X port 5201 connected to 172.20.Y.Y port 51241
[ ID] Interval Transfer Bandwidth
[ 5] 0.00-1.00 sec 39.4 MBytes 330 Mbits/sec
[ 5] 1.00-2.00 sec 38.6 MBytes 324 Mbits/sec
[ 5] 2.00-3.00 sec 41.1 MBytes 344 Mbits/sec
[ 5] 3.00-4.00 sec 34.2 MBytes 287 Mbits/sec
[ 5] 4.00-5.00 sec 35.5 MBytes 298 Mbits/sec
[ 5] 5.00-6.00 sec 40.2 MBytes 337 Mbits/sec
[ 5] 6.00-7.00 sec 42.6 MBytes 357 Mbits/sec
[ 5] 7.00-8.00 sec 38.5 MBytes 323 Mbits/sec
[ 5] 8.00-9.00 sec 33.9 MBytes 284 Mbits/sec
[ 5] 9.00-10.00 sec 32.6 MBytes 273 Mbits/sec
[ 5] 10.00-10.05 sec 1.90 MBytes 327 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bandwidth
[ 5] 0.00-10.05 sec 0.00 Bytes 0.00 bits/sec sender
[ 5] 0.00-10.05 sec 378 MBytes 316 Mbits/sec receiver
Keep in mind these are Lab tests (I am like 1 meter away from the AP) and very synthetic in the end, but I would definitely recommend you to upgrade to our latest beta version (and you can go back anytime you need) and see if it improves the speed. By the way, I'm using 80 MHz channels (my neighbors haven't crowded the 5 GHz band, at least for now).
Of course, as mentioned by @MerakiDave, SNR, Signal, Noise, Spatial Streams and the number of antennas are very important (SNR & number of Spatial Streams above everything).
Leo Gomez