I started about three years ago with a Nacra 5.2 after competing once on a 21' monohull in a regatta. My dad had a Hobie 16 when I was very young and I remembered that boat enough to know that a catamaran was in my future. My monohull buddy steered me toward Nacra and much like most of the public, all I knew of were Hobies. I knew very little about sailing - just enough to know that I could get from point A to point B and back again (that's the important part!).
The 5.2 I bought needed a lot of work because it had been sitting for 9 years in someone's backyard. I got it for $900 and enjoyed it so much I probably ended up putting $5000 in that boat. I have since moved up to a Nacra 6.0NA to continue to feed my addiction and drain my wallet. I was getting to be a serious contender with the 5.2 but the 6.0 set me back for a while. The 6.0 has been an incredible learning curve because I am a relatively small guy and no longer can I manhandle the boat with my weight. However, it's starting to come around and with these new sails and a lot of knowledge on how to depower a boat. I hope to be in front again now!
Learning to sail on a catamaran is totally dooable. You just need to be sure you know a couple of key things and while sailing (any boat for that matter). This is a great forum to learn about these things and there is plenty of reference material available.
1) wear the safety gear
2) know how to right a capsized catamaran. There is a special technique to it that can make this less than a 2 minute task - I've seen PLENTY of folks - been there myself - trying the wrong way take 30 minutes or better. You might even want to practice if you have some friends around to help if it doesn't go well the first time - remember that you almost always need a good steady breeze to right a boat on the water.
3) While under way in a stiff breeze, always have it clear in your head what your escape maneuver would be if you got overpowered (steer up, steer down, sheet in, sheet out - all depends on your angle of sail and it's real easy to have an impulse in the wrong direction).
I only had #1 down when I went sailing the first time. Initially I spent a lot of time capsizing and stuck with the boat on it's side before I found this website and the material! Good Luck and enjoy the ride!