First, I write this for everyone else who reads this: 12.04 is in beta testing and is not ready for production use! It should be installed with the understanding that it contains bugs and some of those might cause very serious problems, including the loss of important files, including programs and data. It's a very good beta and the bugs are being worked-out quickly, but I'd recommend that if anyone wants to test it, don't upgrade 11.10 but instead put 12.04 onto its own partition. If your testing involves upgrading 11.10, you should make a full backup first. (Lest it sound like I represent anyone else, I don't work for Canonical nor am I involved in any way with the development of Ubuntu; I'm just another beta tester.)

Second, however, Yossile is right: your data and the settings for your programs should still be there, so when you reinstall them they should work as you are accustomed. Unfortunately, it'll take you some time to reinstall them, hopefully not too long. I hope the process won't be too painful. I'm sorry this happened.