I, personally, love Costa. They're Italian, so they don't do everything the way the other lines do as far as catering to clientelle. However, the staff is amazing. They all don't speak English really well, but they will try to help. It's amazing how much a smile will make their day. The food has a definite Italian twist. The ships are very clean, very unique decor, vibrant colors, large cabins (even the insides). We've sailed on them 4 times, and I'd go more often if they spent more time here. When you leave a port, they play Dean Martin's "That's Amore". They have toga night on the last night. They have some great activities, like their passport night. You get a paper passport, then they set up different areas to sample food/wine from the region and stamp your passport.
The things that turn most people off from them are: they are VERY family oriented with LOTS of children on board. Every announcement is in 5 languages and you have to wait through each language outside in your life jacket for muster. They do not pamper you like most cruise lines. I don't want to make it sound like they don't do their job, they do. They just don't go overboard. If you approach them right (not yelling or demanding), they will totally go out of their way. If you treat them, like I've heard far too many passengers treat them, with disrespect, you aren't going to get the time of day from them.
They have the most efficient embarkation of any cruise line we've sailed on. Instead of giving you your shipboard card when you're standing in line, they just take your credit card verify your passport and you're on your way. Your shipboard cards are awaiting you in your cabin. Even if you don't have your card, you can order drinks at the buffet or bars by just signing your cabin number.
Here's a link to the Mediterranea pictures. Don't know why I didn't upload the Magica, guess I need to do that. She was beautiful, too!