After working with Gnucash for a while, I decided that I wanted something different. I don't want a GUI to get in my way and I want to keep the file in an easy to view format. After looking through many different open source accounting packages, I decided on ledger.
LWN has an article about their shift away from QuickBooks for various reasons. One of the comments in that article mentioned that the Software Freedom Law Center uses ledger or hledger for its accounting. Here's the post describing SFLC's usage of ledger.
I was looking to track personal finances with a command line tool and ledger fits the bill. It's a double-entry accounting package that uses a plain text file which I track in git. It allows me to easily use the accrual method with minimal fuss.
I currently use Wiegley's C++ version, ledger. I would like to use the Haskell inspired version, hledger, but it is missing some of the features from the C++ version such as budgeting and forecasting.