I have 6 for personal use, which makes accounting so much easier. I assign a budget at the beginning of the month and at any time I have a good overview of how much I spent for that duration.
To illustrate, this is how I split my accounts:

• personal expenses
• household budget / groceries. This one's a shared account with my GF
• savings
• credit card
• rent / utilities. Pay in a fixed amount each month, slightly higher than average spending and then not get shafted when insurance or a high electricity bill is due.
• work travel. This one is the exception. It's empty unless I travel somewhere for work, then I top it up and at the end I copy and paste all my expenses from this account for travel reimbursement

I spend less than 15 minutes each month on accounting and the only downside is that I have to set up several budgets and carry a round several cards to pay with. Once a year I go through the accounts and adjust budgets if necessary.