Talk Talk line management seems to be pretty aggressive and I think Sky is as well, but at least Sky will change it, Talk Talk when asked, don't seem to care.
TalkTalk will switch off DLM if you ask on their forums...shock horror! I had it switched off within 30 mins of asking 
Phoned up Talk Talk last year on behalf of someone asking them about this and the person on the other end did not have any idea what I as on about and said that the system was automatic and that it could not be changed.
Talk Talk did not used to have a DLM system, because before that this person had a okish connection. thankfully they seen sense and gave TT the big heaveho even if it did cost them
[]One doesn't need to be a TT customer to be able to read reports by respected consumer champions and to be able to fathom out the drawbacks of Full LLU.
Actually going on full LLU with Talktalk has more advantages than drawbacks.
PROS
Significantly lower cost for BOTH broadband and tel calls
One bill for both services
ISP cannot blame BT for broadband/tel service faults (unless line physically is faulty)
CONS
Not so easy to leave
In a nutshell, if you plan on changing ISPs every 2 weeks or have a gypsy lifestyle then full LLU is a definite no-no. However if you want the cheapest quality broadband with cheap UK/intl/mobile calls then going full LLU makes much more sense. In my case, i pay TalkTalk 25 notes a month for 18 meg broadband (fully unthrottled with at least 100gb data per month), unlimited UK landline/0870/0845 calls and 500 mins of landline/mobile calls per month to 100 int'l countries. Try getting all of that from BT for 25 quid a month...you're more likely to get the middle finger from them!
You get 18 megabits because you are lucky to live somewhere that is close to the exchange. i did see someone on a TT connection that had 18 megabits and they lived around the corner from the exchange, but not in this town.
As for price, I still prefer to pay a bit more and have the choice to leave without any hassle if I so choose to.
I am happy with the service I get, better than the service I had with Bt, which is not difficult and no contract, I can leave when I like if I want to, which I don't
I am not into this putting your eggs in one basket, done it once with Bt, Mobile, home phone and broadband, not keen on doing it again.
As I can afford to pay the extra I will do so, if it comes to the time where I have to go for a cheaper service, it still won't be fully LLU.
Adrian
Desktop machine now powered by windows 7 pro 64bit , laptop by ubuntu
On ADSL24 using C&W network.