I never write anything in my checkbook, as almost every transaction is an automatic bill or a debit transaction at the grocery or somewhere so it wouldn't help me any. I do however, balance and reconcile my accounts on the computer after every day that there are transactions. I pretty much know to the penny how much is in every account at all times. The idea with 'balancing the checkbook' is to reconcile an 'up to date' balance so you did not have to wait until your monthly statement arrived in the mail, that system is obsolete now.
My wife, however, does still 'balance her checkbook' she likes to write it all down and do the math and have it with her if she ever needs to use the account, then again she doesn't religiously get online and update our quicken accounts like I do, so there is benefit to her that would not help me. I'm glad she does it, even if it appears tedious to me, it helps her and the more involved in her finances she is, the better.
Cheers,
Scott