I've used GNUCash and would recommend it. It works very well for me. I especially like that you can schedule transactions and enter new transactions based on similar ones from the past. It is also very customizable and provides a wide array of useful reports/statements. Plus it's absolutely free and open source.

The only downside I can think of is that the UI is not particularly beautiful. The emphasis is on function rather than looks. I have to say though that the charts since the last update have improved immensely.

Also, although you can use it with a flat file (XML), connecting it to a database (such as MySQL or PostgreSQL) is a much better choice from a robustness, scalability and data security perspective. This is trivial if you are tech savvy but can be a bit intimidating for other people.

Disclaimer: I am not really comparing GNUCash to anything else out there. GNUCash was the first accounting software I used and I fell in love with it. Been using it about 3 years now. So there is a chance that this is a case of "he who does not travel believing that only his mother knows how to cook good food".