My Gen4 system was installed in Oct. 2012. I was getting the "up to" speeds fairly consistently for several months, but now my speeds are very erratic. Wi-fi is not a factor as I am using a cat 5 cable from the HT1000 into my Time Capsule and then a cat 6 cable into my Mac.
From HughesNet's speed test:
05/15/2013 21:20:54 1315 875
05/15/2013 20:54:07 1013 869
05/15/2013 20:34:03 288 950
05/15/2013 17:11:41 9697 874
05/14/2013 23:22:02 707 888
05/14/2013 23:08:29 423 570
05/14/2013 21:05:06 2781 895
03/18/2013 21:49:51 8318 672
03/17/2013 00:41:20 697 1011
03/16/2013 22:03:34 3155 943
03/15/2013 20:47:47 590 946
03/05/2013 02:15:29 1155 850
03/04/2013 20:50:30 8239 689
03/03/2013 20:50:31 400 620
02/24/2013 19:16:19 10359 876
02/24/2013 19:15:23 7408 742
02/16/2013 21:24:20 9199 759
02/04/2013 08:02:14 10158 1006
That graph is from a 6 MB download from testmy.net and is typical of how Gen4 is currently performing for me.