I use online banking frequently. Not just to check how much money is in the bank. But also to make sure that my transactions went through properly and to make sure there are no unexpected transactions.
I also use it to get my statement online instead of on paper. I download the statement onto my computer and keep it in Neat Digital filing system. Also my credit union lets my have free online bill pay by using online banking instead getting statements in the mail. The online bill pay saves me on stamps and checks and can make sure my bills get paid on time.
I also download transactions to use with my bookkeeping (Quickbooks).
About those unexpected transactions – I recommend be very cautious about giving away credit/debit card numbers or bank over the phone. If you do make sure you initiated the call and not someone who called you. Also when using online, make sure it is a company you trust and over a secure connection.