DH bought ab roller years ago and has yet to use it. I tried it once and would say, yes, it is more fun, but you have to watch a video while doing it (at least until you learn the program) and I already have my own exercise routines.
At this point in my life I refuse to lay on the floor for any exercise, so if I was working on my abs I would use this instead.
I heard somewhere that the ab roller can cause problems for your back.
My suggestion would be to get an exercise ball, the big rubber balls that usually come with a foot pump and poster containing different exercises. I love mine and use it A LOT. There are a ton of different exercises you can do on them.
Get the right size for you, keep it properly inflated, and pay attention to how tight you keep your abs for doing the exercises.