There are a number of users who are using the CGN3 on the forums here, with the new ultimate package (the 250 speed)
With it provisioned properly, and either in gateway or bridged (with the right router), have been able to get the full speeds..
So its not directly that the modem can not provide the speeds.
(now, the wireless on the unit in gateway is another issue, where Kiwi is correct.. isnt that great.. but that doesnt directly effect the capabilities of the speed the unit is capable of)
I am wondering if the modem isnt provisioned properly?
As well.. if you just picked it up.. it MIGHT not be on the newest firmware. There were some dropout issues on the last firmware when in bridged. There is a new firmware out which seems to fix it. You could try to contact them and see if they are allowed to push out the firmware manually now.
If not, most users reported getting it in 4 or do days after picking it up.