I had major issues with TalkTalk support. If you ever are in need of support it takes a while to get past the script monkeys before you get to someone who knows what they are talking about. I wouldn't touch TalkTalk again if they offered it to me for free for life.
I am with PlusNet and they have been the best ISP I've used since the early days of PIPEX (before they got ruined by all the take overs).
As for Plusnet traffic prioritization knocking a bit of maximum speed? Never ever noticed it. (But then I did go from a 2meg ADSL to a 70+meg FTTC/VDSL connection).
I do have a fixed IP using their one off payment.
I did use their pro-package (£5 a month extra) but recently switched that off and I've seen no noticeable drop off in performance.
I'm doing a lot of IPTV streaming at the moment for 'work' (really !!), and that has pushed my monthly average up to around 200-250GB of traffic with a peak last month of over 450GB and not a peep from PlusNet about usage. Truly unlimited.
PlusNet support is far superior IMHO but I am aware of increased delays in getting through to them if what I read online is to be believed. I had a BT line fault a couple of months back and was resigned to sitting on a call for 40mins only for support to answer within 5 rings. 1 call, engineer booked, offline for 5 days due to BT, not Plusnet but they kept me informed daily, and got back to me post fix several times to confirm line was performing ok. Even if you do have to wait to get to speak to them, they are UK based and it doesn't take as long to get to someone who knows what they are talking about.
I just can't justify paying a Zen / AAISP type of rates, when I get the performance I do from PlusNet.
All the time BT management stay away from PlusNet and let them run things they way they are doing right now, I will stay with PlusNet. The instant BT interfere, I'm off.. BT are 2nd behind TalkTalk of my providers to avoid.
Sky aren't even on my radar...