So you've upgraded your virginmedia connection to 30Mbit+ and your wireless-N isn't quite living up to your expectations?  This is the issue I had.. the internet speed was great.. getting a constant ~3.6Mb/s but if I transferred any data over the wifi eg streaming or copying, the speed would be very very erratic to the point of being slower than 802.11bg.

I read a lot of forums (including Virginmedia's, see this thread or this thread) with lots of people experiencing the same thing (amongst plenty of other performance issues), so I decided to create this page as no-one had actually gave any concrete solution.

After a few days of trial and error I found the combination that worked for me:

Security Mode: WPA Auto

Channel: 64

802.11 mode: Up to 300 Mbps

802.11N Band: 5 Ghz

The downside of this is, if you have any 802.11bg devices, they will not be able to connect or even see the network.  You can overcome this by either purchasing 802.11N adaptors or a cheap access point/wireless router that supports the slower 802.11bg 2.4Ghz.  I had my trusty old Netgear DG624 to hand due to the upgrade :)

EDIT: Boooooo!  The wireless on the superhub is flaky at best.  The N speed is not constant.  I have to do a null change in the wireless settings to correct that, which only lasts until the router is rebooted, which will happen when the router drops the wireless network.  Streaming video is just a no go, even at N speed!!!  So for me, the wireless is throttled to 2.4Ghz 54Mbps :(

Other than the wireless, everything else is OK.  Internet connection is uninterrupted and at full speed and the internal wired network runs smoothly and is able to stream without an issue.  So I guess the above is a bit of a moot point.

EDIT (29/05/2012) YAY! \o/ Just had a new Superhub delivered and using kernel 3.4.0, I have stable and fast N connectivity. 20Mb(ytes)s throughput! Nice!
However, the router will kill the wifi if (for example) there is a lot of output going to stdout :(

EDIT (04/10/2012) GAH!  VM updated the firmware to R36 a few weeks back which seems to corrupt "large" downloads.  The work around is to put the hub in "modem mode" and use a separate router.  There are several threads about this on the VM forums.