We spent two weeks on Seascape in February, had an amazing time. Buffet could get really busy at peak times, after a few days we just avoided the peak times, admittedly that wont work for everyone.
Pool deck on seadays again got really busy but we managed with it.
We found the main dining room food very good, one or two dishes in the whole two weeks were maybe average but certainly not bad. Portions weren't huge but again never left hungry.
I saw reviews about miserable staff, never encountered any, odd time a barman could be a little abrupt but they were generally rushed off their feet so this is understandable.
Ship itself is stunning inside and out, personally if you enjoyed Virtuosa I cant see you not liking Seascape, incidentally we are on Virtuosa out of Southampton end of June, our first time on her.