A lot of people think checks are too much of a hassle, but many people still don't trust PayPal, online billing, or credit cards, so they are still widely used. If you want to accept checks, you should always have a disclaimer that the items will not be mailed until the check clears your bank, and you should also state that you charge a fee if their check bounces. A much more reliable stance would be to request a money order or a cashier's check, both of which are paid for in advance, so they will not bounce.
If you think you may do enough sales by check, it might be worth your while to get a PO box. I have one that is the smallest that the Post Office offers, and it only costs me 26 dollars a year.