Only issue i have with the Nationwide is that our branch often has long queues on Saturdays. Having said that i rarely have the need to go into the branch.
Other plus points,
Nationwide credit card has Zero commission on Foreign transactions. I did and experiment not so long ago buying two items in the US on the same day and the Nationwide card provided no commission and a better exchange rate than the other card.
Theyre quite flexible with terms on their mortgages. For example the tracker im on only allows an over payment of £500 per month, obviously if you keep over paying at some point they will drop your repayments to match your term again, either on a rate change or anniversary. They will stop doing his if you ask and you can then get yourself into a scenario where your over paying by more than the allowed £500 overpayment per month without penalty because they havent changed the amount they request from you
ohhh and ive only had bad experiences with the Halifax