Just off the Wonder less than a week ago (our 5th cruise on her). She's a fine ship and in good condition. There is some wear and tear - think of your brand new car a year after you bought it - still pretty nice but the "New Car Smell" is gone. It is a 90's model so some of the "cool high tech stuff" is not on the ship. If those items are important to you then the Wonder is not your ship. If you want good food, good service, smaller crowds and a great crew then the Wonder will fit your needs quite nicely
We noticed a lot of replaced carpet, and Palo has new (different) carpet and some new tile. Shutters was updated to the "Library" vs. the Where's my pictures scavenger hunt. And Shutters and the stairway down to midship has new carpet. The atrium still has two staircases which is nice - will reevaluate once I sail on the re-imagined Magic later this year.
Three areas where the Wonder has more room than the Classic Ships: Dinning Rooms, Staterooms (at least in cat 9) and the Walt Disney Theater. The pools are also more appropriately sized for the crowds than the new ships too (but they are to small too - but you're on a ship ... what do you expect
We had a great 5 nights onboard. The crew is first rate. It does not have the bells and whistles of the new ships ... but for the most part, that's NOT why we cruise. We enjoy relaxing and being treated like "royalty"

There are plenty of activities on all days. Would have liked to take the pace a little slower, but they kept planning activities that I wanted to participate in