My husband and I agree with Donna. We enjoy dining in the dining room and having the same waiter and assistant who get to know you and can anticipate your wishes.
We frequent the Windjammer for breakfast, lunch and snacks (how do our kids find the ice cream machine so quickly?!).
Also, if you enjoy meeting new people or would like to be waited on, you may want to check-out the dining room for breakfast and lunch. During breakfast and lunch it's "open seating" so when you arrive (unless you request a private table) they will usher you to a table with others coming in at the same time. It's a wonderful way to meet fellow passengers and discuss our favorite subject -- cruising!
Either way....dining on a cruise ship is so much better than land. You don't have to decide which restaurant to go to, or make reservations, or look at prices on the menu, wait for the check and you can't beat the view.
Also agree w/ Donna & HappyJan...... the dining room is my favorite thing on the ship. I love sitting at a nicely set table and being waited on. Meeting new folks and making new friends is a bonus. For me a buffet like the Windjammer is just the same old same old. I can, and do, wait on myself at home. That said, if you just can't bear to change clothes or hate to waited on or like to eat in 30 minutes, you are welcome to eat dinner in the Windjammer.