I used PAF for many years, then about three years ago decided to look around to see what was available. I started by looking at the free offerings, which at the time were RootsMagic and Legacy. I live in the UK, and Roots Magic had a UK version. I felt Legacy was slightly better, but very US oriented (particularly wrt place names). RootsMagic at the time offered a read-only version which could be put on a disc to distribute the tree, which I thought was a very good feature, but I think they may have discontinued this. Roots Magic had better integration with the Family Search site than other programs. Just as I was about to make up my mind I discovered the Family Tree Maker site and watched some of the tutorials, here: http://www.familytreemaker.com/Learn/Tutorials
I came to the conclusion that it had a more professional feel, and it handled media and sources better than other programs did at the time. In the UK it comes with several months subscription to Ancestry (the length and type of the subscription is the main difference between the versions - all have the same program), and at that time could be obtained cheaply from Amazon. This meant I could buy the program for less than the cost of the included subscription, so I decided to try it out. I like the program a lot - especially the integration with Ancestry.co.uk. (e.g. when you find a census entry you go through a short dialog to say what you want, then the program downloads the image and creates source citations for name, sex, residence etc. for the people you selected). The latest version includes the ability to keep your tree in synch with the tree on Ancestry - although this is a fairly recent feature and can still be buggy. Most of the people who complain about the program on the forum seem to have very large trees (tens of thousands of ancestors), so I wouldn't necessarily recommend it if you are one of those. I have about 500 people in my tree and so far it seems to perform OK. The current version of FTM 2014 has just been released in the US (and is about to be released in the UK), but the price will probably drop in a few months (in the UK at least, if it follows the pattern of previous years). FTM will read in a PAF tree directly, by the way.
My advice would be download copies of any free programs you are interested in and try them out but also take a look at the FTM tutorials. Then choose whatever suits your individual likes and needs.