We have 3 "demand" accounts (1 credit union, 2 money market) but only write paper checks on the odd occasion when we cannot use our free, online bill-paying through the credit union. Lots of savings in postage!
Unfortunately, the fields that get filled out on-line, don't allow enough space to put all the information on the check that some entities, such as the IRS and MD tax authority, require. This has resulted in stupid stuff, such as our quarterly estimated tax payments being credited to me (not spouse) even though we file a joint tax return. The tax people didn't see both SSN's on the check, thus, "Hey! Only one of the Feet is paying his/her taxes! Let's send the other one a Threatening Letter!"