Forgive me if this has already been discussed but searching on B doesn’t work.
The question is what does B not do that we all desire in a perfect bank account?
It is linked to a Mastercard that has no foreign transaction fees (except cash withdrawals)
Joint accounts
CASS
Imaging cheques
Pots
Interest
Pending payments
Apple and Android pay
Overdrafts
Physical banks to pay in cash
A lot of discussions was in these threads about B 
Yeah, I quite liked B when I tried them, to be honest. They even have a credit card with a pretty low interest rate and fee free foreign transactions, on top of all you mentioned.
My issues with them:
)Remember B is a product of what is essentially a UK regional bank (CYBG), centred in the north of England, and Scotland. There are branches in London and elsewhere but these are few and far between. (I don’t know about CYBG’s arrangements with Post Office.)
I know, and I was fully aware when I signed up, and am not complaining. Just responding to the point regarding physical banks 
I signed up to give them a go thinking that they were going to be somewhat similar to Monzo in their offering. However, i found they still act as a legacy bank e.g. delay in transactions appearing, still have to wait for pin in the post etc and the app is quite messy. The biggest let down was their customer service - my first experience with them was trying to pay a cheque in through the app. i thought all had gone well but the following day i get a notification saying I have to go to their bank to pay it in with no explanation. After the notification disappeared I can’t even see a record of this in the app so lucky i didn’t miss it.
No intention to stay with them and will close the account
Speaking personally and not as part of the Monzo team, I’ve found B to be among the better offerings from the legacy banks. I actually worked for Clydesdale Bank a few years ago, so I’m familiar with how their back end works and I know a few people at B. They seem to straddle the line between legacy bank and something like us, in my opinion leaning more heavily towards a legacy bank; they still run on all the legacy tech that the rest of them do.
Right now, they serve as my back-up account; I don’t have any regular deposits with them and realistically the only time I’d use them is if I’d lost my Monzo card and needed to use a card in the day or two before I receive a replacement.
That said, I really dislike their app. I can see what they’re trying to do with it, but the colour scheme and general layout of things doesn’t really fit my idea of good design.
Pretty good telephone banking experience though!
It’s still legacy rust at the end of the day. That’s enough to put me off personally.
What does that mean to you though?
It means my money is handled by modern systems developed using modern best practices, instead of a rusty “magic box” inherited from 40 years ago, so less change of anything going wrong and if it does wrong it will be easier to fix than on a legacy system. It also opens the door to innovation while legacy banks are stuck in the past.
Why do we call it B… why can’t we say the name? 
B is the name.
I do wonder what they were thinking. SEO must be a nightmare!
That doesn’t really hold water though as sadly Monzo hasn’t been the paragon of reliability over the last 12 months.
The advantage of building stuff new is that you can easily add new features and take advantage of new technology that would take legacy banks a lot of time and effort to implement - it’s not necessarily better for reliability as nobody has any ideas what sort of bugs might rear their ugly heads.
There’s a reason that the ‘magic box’ is still there in legacy banks, it’s because it rarely breaks!
FX free MasterCard? They charge 2.75%
And their web app is 10x better than the mobile app .
Their credit card is fee free for purchases
Oops, I knew that… I thought you were talking about Barclays
Paid in a cheque today using imaging in the “B” app. Money was in my account within a couple of hours.
Very impressed.
Why cannot Monzo do this?
There’s a massive thread about why cheque imaging was cancelled. If you search at the top you will find it