A lot of the older versions of FTM were just yearly updates, culminating in I think the 2006 version. It was always a very stable programme and used by lots of people who are very happy with it. 2008 was introduced using completely new architecture and code to work more efficiently with newer more modern computers, it wasn't very well received. A lot of people, including myself, bought it only to find it very buggy and extremely slow. Also the completely new look didn't go down well either. The next version, 2009, was offered as free upgrade to 2008, bringing back some of the features previously available up to 2006, but not in the 2008 version. I've got used used to 2009 now and quite like it, it is still quite slow, but that's more to do with my aging computer than anything else. 2010 is a further update to 2009, so they are continuing the yearly update process as before, but I will wait until 2012/13 comes out before I indulge again.
