I use my debit/check card for just about everything and almost never have more than $20 cash on me. I will run my card for a $2.00 purchase.
I use Mint.com and check it at least once a day. I check that against my monthly statement. Yes, I still request a paper statement. I don't just trust that all of my money is there and every transaction is valid.
So, no I don't enter everything into an old fashioned register, but I know exactly where every penny goes.
Again, her not cashing a check hasn't been a problem. I brought it up because I could see how it could easily become a problem and it just surprises me that people wait that long. I tend to deposit them almost immediately as my bank has a feature to electronically deposit via cell phone or ATM.