CM600 on TWC has extremely slow speeds after switching from an Arris brand

I've always been a loyal Netgear router man.  Since Time Warner Cable has increased the speeds in my area to 300 megs I had to upgrade my modem from an Arris 6141 to the Netgear cm600 because the Arris would top out around 100 megs.  I Since I had such good luck with the routers I thought I'd try netgear modems.  Hooked up the modem like I was suppose to, called TWC to activate it....they did. I got on the internet and did the speed test through speedtest.net and was only getting from 2 megs to 20 megs.  Tried it 4 or 5 times.  Rebooted my computer and tried it a few more times while I had TWC on the phone.  Same thing.  Slow speeds.  The rep asked if I wanted to try the Arris again and when I did the speeds were back up to normal....around 90-100 megs.  I've got a service man coming out next week....is there anything I need to make sure he knows when he gets here so i can get this solved in one visit? Or is there anything I try over the phone with TWC before the tech gets here next week? 

I tried connecting to 192.168.100.1 when I had the cm600 activated and I couldn't...It wouldn't connect to the IP site, but it would connect to other regular sites.

I'm running on Windows 7 OS.

Any help would be appreciated.  Thanks

Thanks.