Gigablast consistently coming in WAY short (<50%) of total speeds

Signed up for Gigablast about 4 months ago.  When I first signed up, I was consistantly getting 900+ Mbps up and down.  I work from home, and I move a lot of data around, so the speed was a godsend.  It was easily the biggest quality of life improvement I've have in my job, ever.  

The last 6 weeks, however, have been total lackluster.  My speeds will never go over about 480Mbps.  I noticed the drop in speeds right away, and I'm well aware of how speeds can fluctuate based on congestion, so I've been monitoring it several times a day.  It doesn't matter what time of day I test my speeds - 2 AM, 5:30 AM, 9 AM, 3 PM, and 11 PM, weekdays and weekends - it's always between 440 Mbps to 480 Mbps, down and up.  I've been monitoring it for 4 weeks, every day, and no change.  

Since I'm sure it'll be asked - yes, I've rebooted machines, the router, and the modem.  The PC I test with is hardlined into the router, and yes, I've bypassed the router on the test PC as well.  It's definitely not my home network.

Anyone else with Gigablast experiencing less than half the speeds they are supposed to be getting?