DH & I did a Carnival cruise last month. Like you, price was right, and it was a good option to try it without kids. We were on the Elation, not the Dream
I recommend you go into it expecting it to be different and to be LESS.
It costs less, and in some areas things just are less.
I still had fun, and feel I got my money's worth.
It just reinforced why I pay more when I go on Disney
I did think the photographers were better on Carnival.
The dinners were equivalent to Disney. Our servers were great. It was odd not being able to order drinks from the servers, they had to send a bar server over for drinks, but after the first meal, the bar server would automatically come over.
Buffets were okay, really noticed less fresh fruit than on Disney.
The shows were not as magical, much more Vegas style.
Disney's deck party was far superior.