This morning I went to the Joel On Software Fogbugz 6.0 talk that was hosted in Cambridge. It was an interesting presentation on the new features and capabilities of Fogbugz with some nice little anecdotes dropped in for good measure. Most of the time was spent on the new Evidence Based Scheduling feature which is quite nice and will help with estimation accuracy., taking some of the uncertainty away from that aspect of the development process.
Fogbugz makes a good thanks to the AJAX interface, although I won't say it looks awesome with the default skin. The AJAX features certainly makes the user interface have less friction for use and has some nice touches to minimise clicking and the such. It would probably make even more sense as one of the Adobe AIR type apps to make it integrate into the desktop or something along those lines with gadgets.
The thing that was lacking for me unless I am really weak with my Google searching is bug relationships. You can create links to other bugs and they are listed in the bug report, but in systems like Bugzilla you can have a rich relationship. This means you can create dependency graphs and define the types of relationships.
I'm afraid I would not recommend spending money on it for my situation. It is a tool that works best for developers and in the development situation, and not a company-wide tool (unfortunately, although it could theoretically work), but I am all for making developers lives easier. It is just I feel that if you have a technically adept development team then they will be capable of accomplishing the same goals with other tools. This is especially necessary as most development teams can never get financial approval for new or better tools (unfortunately it is still what I hear from most people since most developers have given up asking).
I suppose what I am getting round to saying is that if you are using Subversion or a supported version control system, you should try out Trac. The integration between source control, wiki (documents), issues, and more are excellent (and it looks good). It is a developer's tool though rather than a forward facing tool for customers, but it will improve the development team's workflow. It can do more or less everything Fogbugz can do with the default install plus the whole host of Trac Hacks. I've blogged about this tool before.
I must admit I am a big fan of Bugzilla because the bug reporting system is so rich and configurable. If it had the Subversion and plug-ins equivalent to Trac then it would be amazing. As things stand though Trac does work a treat, hell even open-source projects are using Trac to host their websites like OpenSceneGraph.