I've used both JoomlaPack (AkeebaBackup it's now called) and Xcloner. JoomlaPack (Akeeba) is free, so you can't knock the price. It also has the ability to include an installer for loading the site onto the destination server, nice. I've used it many times.
However, my preference is Xcloner. It's a little more "programmer oriented," so its interface is s a little simpler and quicker, in my opinion. (Maybe that's just because I started with Xcloner.) Also, instead of a clunky installer package, Xcloner gives you a "restore" feature consisting of 2 files:
xcloner.php
tar.php
To restore, just include your Xcloner backup file alongside these "restore" files in your public directory, and point the browser to the "xcloner.php" file. It will ask you for database / ftp information, unzip the file, import the database, and adjust configuration.php accordingly. It also gives you the ability to extract the files directly (via PHP), or via FTP, depending on your server's particulars.
