We are seasoned cruisers, having been on several previous Celebrity cruise ships and others. We'd read scary reviews of the Infinity, but goodness knows why. It was very enjoyable. The staff were unfailingly polite. The tours were well thought out and full of information. The meals were splendid - always lots of choice and very balanced (though Oceanview Café staff were struggling to provide a good service level, we found). Cabin had everything we needed (though the balcony was so salt-encrusted that we couldn't really use it much).
It's not the biggest, glitziest ship in the fleet, but the amazing navigation skills and willingness to resolve issues more than made up for that.
We heard a few guests being extraordinarily rude to very patient, polite staff about things like "flowers not being out in the gardens we visited" (well, it was nearly October by that stage...). But mostly the passengers were relaxed, cheery and good fun.
Well planned, loads of space, comfy big bed, they even provided a kettle and tea/coffee for the room. Balcony needed cleaning of thick salt from recent weather, but otherwise fab.