Got new fast internet, but steam download speed crazy inconsistent?

Hello
So I just got the comcast blast deal, 150mbps, and got a new router and modem for it as well. Speeds seem pretty high.
But when I tried downloading a game on steam http://i.imgur.com/NpM47Hc.png It went from downloading at 15.0 MB/S to 0.... I was kind of expecting a consistent speed, especially since I'm the only one using it currently. Granted I'm not exactly sure what disk usage actually is? And it moved around a lot too. Anyone know of a fix??
Thanks
edit: Tried with ethernet, got same results. Also tried on origin, speed was a bit slower, but completely consistent speeds and no large drops at all. So steam is the problem? And if so, is there a fix??

I've been having a similar problem lately. I think it is either the server can't keep up or some issue with your disk. You downloading to an SSD or is the drive a mechanical? Is it your OS drive too?

SSD, windows 8.1

Steam used to never pull more that 20 down for me on a 100 down connection.
One thing that really did help me however was changing my steam download server.
In my case from London to Manchester or but if you can find one in a less populated area / country I'd give that a try and you ought to see an improvement.

try setting up a PF sense router with random hardware. I know after switching from Linksys firmware to a PF sense box my download speeds seem much better. (keep in mind that my linksys may have been over heating)