Well, you can still make them look good, even in slim cases. I just converted 4 of my Wii games to slim cases (Fire Emblem, Mario Kart, RE4 and RE:Umbrella), and they still look pretty nice.
Instead of typing a name on the spine, however, I took the original spine logos and resized and/or rearranged them to fit the spine. I never really liked plain text on the spine, especially considering the spine is the part that is going to get the most eye time. I mean, I rarely pull out games just to look at their covers, but I always look at them on the shelves.