I'm having similar problems as the OP. 75/35 package. Speed seems to fluctuate with time of day. I've also noticed increase packet loss and latency. Bypassed the router during testing and tried multiple workstations. Network cable from the ONT. I think a larger issue is at play- my problems started in Q4 2012.
::.. Internet Speed Test Result Details ..:::
Download Connection Speed:: 82550 Kbps or 82.6 Mbps
Download Speed Test Size:: 68.9 MB or 70528 kB or 72220672 bytes
Download Binary File Transfer Speed:: 10319 kB/s or 10.3 MB/s
Upload Connection Speed:: 4568 Kbps or 4.6 Mbps
Upload Speed Test Size:: 2.9 MB or 2944 kB or 3014656 bytes
Upload Binary File Transfer Speed:: 571 kB/s
Tested At:: »TestMy.net
Test Time:: 2013-04-18 22:33:41 Local Time
Location:: Perris, CA US >> Destination:: Dallas, TX US
TiP Measurement Summary (Download):: Min 39.75 Mbps | Middle Avg 84.07 Mbps | Max 88.26 Mbps | 45% Variance
TiP Data Points:: 85.25 Mbps, 84.43 Mbps, 84.02 Mbps, 84.02 Mbps, 84.02 Mbps, 84.16 Mbps, 84.29 Mbps, 79.68 Mbps, 83.89 Mbps, 88.26 Mbps, 84.16 Mbps, 84.29 Mbps, 83.49 Mbps, 83.35 Mbps, 85.25 Mbps, 83.89 Mbps, 84.02 Mbps, 83.89 Mbps, 39.75 Mbps
More Stats:: »testmy.net/compID/159159870594
User Agent:: Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.31 (KHTML, like Gecko) Chrome/26.0.1410.64 Safari/537.31 [!]
Checking for Middleboxes . . . . . . . . . . . . . . . . . . Done
SendBufferSize set to 
running 10s outbound test (client to server) . . . . . 28.87Mb/s
running 10s inbound test (server to client) . . . . . . 29.82Mb/s
------ Client System Details ------
OS data: Name = Windows 8, Architecture = x86, Version = 6.2
Java data: Vendor = Oracle Corporation, Version = 1.7.0_21
------ Web100 Detailed Analysis ------
Client Receive Window detected at 191232 bytes.
45 Mbps T3/DS3 link found.
Link set to Half Duplex mode
No network congestion discovered.
Good network cable(s) found
Normal duplex operation found.
Web100 reports the Round trip time = 11.84 msec; the Packet size = 1460 Bytes; and
There were 638 packets retransmitted, 2604 duplicate acks received, and 3133 SACK blocks received
The connection stalled 3 times due to packet loss
The connection was idle 0.65 seconds (5.90%) of the time
This connection is receiver limited 6.59% of the time.
This connection is sender limited 64.97% of the time.
This connection is network limited 28.43% of the time.
Web100 reports TCP negotiated the optional Performance Settings to:
RFC 2018 Selective Acknowledgment: ON
RFC 896 Nagle Algorithm: ON
RFC 3168 Explicit Congestion Notification: OFF
RFC 1323 Time Stamping: OFF
RFC 1323 Window Scaling: ON
Packet size is preserved End-to-End
Server IP addresses are preserved End-to-End
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