The 50Mb is great. It's the only one that doesn't have any throttling during peak hours:
Virgin Traffic Management Info
You do need a new cablemodem & router (bit of a bugbear here with my latter - it having a fairly-hefty ACL). I got my upgrade from 20Mb gratis for six months, but I did have to pay for the installation. Don't forget the unlimited off-site storage (V Stuff) & 100 free photos (from Snapfish) per month. FYI, all Virgin accounts get a VStuff/Snapfish allocation (according to a sliding scale) although (as per usual) it has been problematic for many users.
Now all they need to do is up their Usenet retention to something more acceptable - although speed is good, 7 days is prety useless. I recently switched to Astraweb; 717 days, 99+% retention & 20 maxed-out SSL connections for £7? A third of Giganews' price for a virtually-identical service. Pretty-much a must-have...
Edit:
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Oops - sorry if I upset anyone for resurrecting this old post. I just realised my bad!