I'm not on Gen4 but when I hit the cap I get throttled to around 15K/sec with turbopage disabled. The only game I've tried while being throttled was Runescape and it worked, you can also still sign into Xbox Live. I don't get capped very often, but for me getting throttled isn't a huge deal, I'm more annoyed by peak hours. Usually around 7PM-10PM I'm barely able to browse the net and I'm unable to sign onto Live.
I'm not sure, but I think the Gen4 usage meters aren't running (At the time of this post) so there's no way to tell how well it will perform once you get throttled.
Cool, thanks for the reply. So I can suspect the throttled rate will be the same or better on Gen4, that's good. And 15K/sec is still better than dial-up, though some things would probably work better on dial-up still due to latency.