Interesting thread there mike.
Whilst a lot of it is down to your own line conditions there are several ISPs that do indeed seem to be miselling the "Up to 8Mb".
Personal experience of this - of which Ive seen many exactly the same:-
TalkTalk being one of the major culprits.
I was round at a mates house week before last and he asked me to have a look at his connection cause he was having a few problems and "it seems slow".
My mate had been persauded to switch his 2Mb BTInternet connection to a TalkTalk "up to 8Mb".
Line was still syncing at 2272 but speeds were really dire 500-800 kbps!
CS was awful - went round in circles and had their CS cut me off 3 times! - But the jist is they are only providing 8Mb on their LLU exchanges.
My mate is not a happy bunny to migrate a perfectly good rock steady 2Mb connection on the promise of 8Mb to what is now more like a 512kb connection at times :/ (No its not the exchange nor his line).
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AOL seems to be pulling a bit of a fast one recently too. I believe theyre getting their gold customers to sign up to another 12 month contract on the promise of 4Mb speeds.
They appear to be passing the upgrades through to BTw - and the customers are syncing at higher speeds.
But what AOL aren't doing is actually upgrading their customers on their database and leaving them with a 2000 data rate profile at their end.
Any customer who does eventually manage to get through just about every excuse in the book as to why their speeds are still slow - are then told - The AOL system hasnt got a 4Mb profile yet for gold - but you should get it in the next 6 months.
Theres a long thread on some other forum about this.
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I also have first hand experience of Bulldog last year trying to mis-sell me a so called "faster connection".
The indian lady soon put the phone down on me when it became clear I knew a bit about adsl and I was able to question her untruths about what I was being promised.
She actually implied I would get 16Mb on a non LLU exchange when I knew the most they would really be able to offer me was 2Mb which is what they offering non LLU. Despite me already having a 8Mb connection.
If I'd fallen for it - I would have ended up loosing my 8Mb max and going to 2Mb datascream
Another major gripe -
Too many ISPs have also taken the Max upgrades to get their customers to sign up for another 12/18 month contract.
This IMHO is very poor, because the vast majority of these upgrades are at no cost to the ISP.