Just seen this thread and thought I would post a reply as I've been running the Vigor 130 for the last month or more.
The original modem I was supplied was a ECI modem (I'm on a Huawei) which was running with nice low pings and a consistent download speed until G.INP was enabled, after which the ping went up to around 25-30ms and the download speeds dropped off a little. ECI speed after G.INP
http://www.speedtest.net/my-result/4330999252As I didn't wish to buy a Huawei off eBay and run with a hacked firmware but still wanted visibility of stats etc I decided to go with the Vigor 130 having used the 120 for a number of my business connections previously. I'd already contacted pre-sales who said a G.INP firmware was incoming.
Setup was non-existent I just connected it to my line and hooked my router up to it (after having a look through the web gui), line sync'd with no issues and as expected I got similar speeds to the ECI
http://www.speedtest.net/my-result/4335668160 (stats page shows interleaving on my line and Retransmission disabled).
Yesterday I updated to the newly released G.INP firmware (3.7.8.1) using the reset option, stats page now shows I'm running on Fast mode with G.INP enabled. Pings immediately dropped down to 7ms, and sync went upto 71Mb.
http://www.speedtest.net/my-result/4442209993So far all good, no complaints.