The recent upgrade from ADSL24 was actually very positive for me:
* DL sync increased from ~3M to 3.8M
* UL sync increased from ~600k to 950k (!)
* More importantly, stability has
vastly increased and SNR margin become much more consistent.
I guess the differing reports in this thread are down to specifically what equipment the two companies have installed at your exchange, and how differently they handle your line. For me, it's been the end of a nightmare.
I'm on a ~4km line from SSALM, and had been having terrible link reliability since the 21CN "upgrades" there in 2009 - many random desyncs and often dropping when picking up a voice call too. It seemed to be related to the uplink SNR being too low - I would often watch it creep towards zero and the inevitable disconnect while the downlink was still fine. When I complained through ADSL24, all BT would do is increase the
downlink SNR target, leaving me with a line slower but just as unstable. I'd long since given up on ever getting this fixed.
Before 21CN and the new BT linecards at SSALM, I had great reliability - typically several weeks between desyncs. The move from the new BT linecards to Talktalk's has been almost a return to those good old days, only with better speeds. I'm seldom getting more than two desyncs a week, and never on incoming calls. At a wild guess, I suppose the uplink Tx power from this linecard must be higher.
The one downside has been an increase in bufferbloat on the downlink. Netalyzr reckons it at around 2600ms, where previously it was a few hundred (still bad but not outrageous.) Of course, you only see this when you load up the connection. Would be nice to see it fixed though.
To be honest, I had been considering a migration away from ADSL24 - albeit not on the expectation of a better connection. This change made me reconsider.
The other things that were bugging me remain, though. Word from James about what you're going to do about bufferbloat would be appreciated (especially as it's now worse on the new linecard,) as would news of IPv6 dual stack support and the odds of getting a current version of BIND (preferably with DNSSEC enabled) on Daisy's DNS servers. Are you there, James?