I have never read of the Gemini being "unsinkable" as some other boats are labeled (like the Etaps). Given enough wind & waves even these big cats can flip though. Overall, I think the Gemini is a good value for the money - they have made over 300 of them in the last 3 years so a lot of other people must think so too. You might also want to check out the Admiral 38. Catamarans in general make better cruisers and livaboards. No hull lean and space that is set up more like a house than a sub.
Click on the Main Index link at the top of the page and go to the Cruising Multihull forum. You will want to repost this question there as this forum is strictly for beachcats - Hobie, Nacras, etc...
Good Luck,