We were a little apprehensive going onto the Spirit because we'd most recently been on the Epic and thought that the size difference would be a problem. We couldn't have been more wrong - it was delightful.
The boarding could have been better, but this was delayed due to an IT issue that meant they couldn't scan anyone's passes. Once that was fixed, the boarding proceeded at a much quicker rate.
Food onboard was generally good in the speciality restaurants, but was so-so in the main dining room and buffet. But has been the same on other NCL ships - although it's worth noting that at the time of sailing, the Spirit was still using older menus than other ships. This is a significant benefit as there's a few dishes that simply aren't on the new menus but we could get them here - for example, the lamb in Le Bistro. No lobster though, but we weren't expecting any!!
Good cabin, just had fresh carpet laid. No issues with external noise at all.