A couple of small points
... and something to bear in mind - all we're doing is moving the bottlenecks. On 56k the bottleneck was definitely that bit of wire that ran from your PC/Phone to the exchange, very limited bandwidth available there.
Let's say the hardware running a given web server can cope with 1Gb data transfer a second; that's all things considered from ethernet restrictions to the data transfer rate across the motherboard between processors and RAM.
If dial-up users are connecting to that site it can cope with about 18500 users at any given time downloading - which is probably plenty. But get everyone up to 4Mbs and that's oooh 256 users to hit capacity, 20Mbs and it's about 50 users.
Now bear in mind that if it's not a dedicated server it could be hosting several websites, each with several users on at any given time... that's just one factor affecting your ability to download 20Mbs.
Here's another, if you're in a heavily subscribed area, online at peak times, your connection is effectively shared. The contention rate on cable is about 15:1 for residential connections (as opposed to about 40 or 50 to 1 on DSL) so you're likely to get a download speed of about 1.3Mbs max.
However - this only really affects downloads or streaming media. Any (bog standard) web-page will only contain, at most, a couple of hundred Kb worth of content (the page code, linked images, stylesheets and external JS files) and once that's been cached on your PC that's it for that page. 20Mbs down or 1Mbs down, you're talking a difference in fractions a second... but the comments seem to be about download speed rather than web browsing (granted, that's just lots of little downloads).
One final point... latency on cable is _generally_ lower, something to bear in mind if you're a gamer.
I'm not saying Virgin Media is the greatest thing ever and they have got worse since the Telewest days. NTL were the daddy in that "merger"; they still are, and it shows. However... I still think it could be much, much worse... I could still be with BT (they were bad, really bad - right up there with Severn Trent Water and British Gas on the incompetent feckwit scale).