Issue tracking systems for Agile development

I have been using Microsoft Project Server for my softwares projects, but i have never felt comfortable with it even once. I think it is not for software development, but is general purpose project management tool. Software projects are not projects like building an apartment, or making a road, or some others. Especially, agile development is much different than regular projects. We build something in first phase, and then adding new features and changing current modules to make better product, but not final one, and goes on in this way. I gave up my .NET job a month ago and now i plan to migrate back to PHP development with Zend Framework and Ajax technology which can absolutely be called as "Agile development environment". So i needed an issue tracking, or project management software that i can use for my projects to track its progress, roadmap, bugs, etc ... Found out Trac, which uses a minimalistic approach to web-based software project management, has integration with Subversion, has built-in Wiki system and detailed reporting tools. Trac is mostly used for agile web development projects, exactly the thing i was looking for ;) There are alternatives to Trac as well. During my research, i have compiled dozen of open source bug tracking softwares, most of which are minimalistic and simple to use, and for agile web based software projects. Here they are;

• Trac is a web-based software project management and bug/issue tracking system. It provides an interface to Subversion and an integrated wiki.
• Roundup is a simple-to-use and -install issue-tracking system with command-line, web and e-mail interfaces
• Mantis is a free popular web-based bugtracking system, written in the PHP scripting language and works with MySQL, MS SQL, and PostgreSQL databases and a webserver. Known to be good one written in PHP.
  
• Flyspray is an simple, web-based bug tracking system written in PHP for assisting with software development.
• Whups is Horde's bug tracking/ticketing system, designed to be extremely flexible in letting users define kinds of tickets, different lifecycles (sets of states) and priorities for each kind of ticket, and mixing types of tickets into sets of queues.
• EZ-Ticket is a PHP/SQL web based Ticket system, built with SIMPLICITY in mind. Unlike other ticket systems, this ticket system has the same functionality that other ticket systems have, without all the complexity, making it's use efficient and effective.
• Eventum is a user-friendly and flexible issue tracking system that can be used by a support department to track incoming technical support requests, or by a software development team to quickly organize tasks and bugs.
• BugTracker.NET is a free, open-source, web-based bug or customer support issue tracker written using ASP.NET, C#, and Microsoft SQL Server
• phpBugTracker is a web-based bug tracker with functionality similar to other issue tracking systems, such as Bugzilla. Design focuses on separating the presentation, application, and database layers.
• Zwiki Tracker is a simple issue tracking system which can be enabled in any zwiki. Issues can be created via web form, by mail-in, or by renaming an ordinary wiki page.
• BUGS - the Bug Genie is an open source enterprise level issue tracking system, built on open source technology. "BUGS" enhances your development process, by offering an advanced tool to manage bug reports, feature requests and user feedback for your products.
• JTrac is an open source and highly customizable issue-tracking web-application written in Java.