Had one for a year, paid over £600 in fees for direct debits, cash and same day transfers.
They usually contact you asking for proof of invoice if a payment coming in is over £10k, that takes a few days. Money never comes in over the weekend and you must make your payments or any transfers before 3pm if they are to go in the same day.
It is an option for those who can't get a normal account but really it does much business life much harder than having a high street bank. By the way I also had my balance increased to £30k instead of 15k that they state is the maximum in the account at any one time