We use fogBugz here for both bugs and feature requests. Simple, easy to use and very effective.

For project scheduling, we use Excel and schedule everything in week increments.

Inspired by Joel's article Getting Things Done When You're Only a Grunt, I tried to get our team to use FogBUGZ a couple of years ago and thought that it was a fantastic product -- very easy to set up, very intuitive to use, it just worked.  Unfortunately, some of the other team members were kind of lackluster about using it and the boss at that time didn't really penalize people for NOT using it, so it kind of died a slow death.

Then, when the company hired a new CIO-type guy to come in and take over the department, he liked FogBUGZ at first and I thought it might get a second chance, but after a few months, he ended up replacing it with a horrible product from Intuit called "TrackIt" because he wanted all the pointy-haired-boss "employee metrics" type reporting features that Joel has deliberately left out of FogBUGZ because he thinks that tracking people in those kind of ways has too many negative side effects.  (people tend to work to improve their statistics rather than working to improve their projects once you start hassling them about creating too many bugs, etc)

The achilles heel of all defect tracking software is that it's worthless if people don't use it religiously.  This seems obvious, but amazingly, people just don't seem to get it.

In my experience, the main reason that people don't want to use defect tracking software is that they don't want to admit that there are defects in their software!  Seriously.  Some people will literally spend more time quibbling over whose fault something is and whether something is a bug or a user misunderstanding or a poor design forced on them by someone else, blah blah blah than it would have actually taken to just solve whatever problem is being reported in the first place.  These types of people seem to perceive products like FogBUGZ as personal attacks on their competency as developers rather than as tools to help organize all the layers of complexity involved with making good software -- information that nobody can possibly keep track of in their heads and on random post-it notes.  For this reason, defect tracking software that is geared toward creating performance reports on people just makes the situation even worse because these same people who are ruled by their egos will be even more worried about looking bad if the software makes it easy for the manager to compare everyone.

Anyway...*if* you work on a mature, professional team who will use it, FogBUGZ really is hard to beat.  I think it strikes a great balance between being flexible and feature-rich, yet uncluttered and non-intrusive.  I really like the way it keeps a chronological log of all the steps that have taken place in the process of fixing a particular issue, and it does a great job of making it easy for team members to pool their knowledge into one consolidated place.  It is nice that all you need is a web browser to access it so that you can log in from any workstation on your network and even access it from home if you host the installation on the web.  Another benefit to having the bug reports in a web format is that it is makes it easy to insert in-line screen shots and scroll through very long lists with lots of repro steps, etc.  Some other programs such as TrackIt make this sort of information hellish to navigate because you have to fight with/be limited by their clunky interface...

One last point I might add is that if the lack of statistical reporting would be a strike against FogBUGZ in your organization, keep in mind that all the data it tracks is in SQL server, so it would be fairly trivial to make your own reports using some other tool if you really, really had to.   But please don't...

I liked using FogBugz as a to-do list -- I thought it worked quite well.  In fact when some of my coworkers started slacking off on using FogBugz to track bugs as I mentioned in my earlier post, I still continued to use the system to manage my tasks.  One of the features I found useful is the "dispatcho" service that listens for incoming emails, because this actually allowed me to just email notes to FogBugz and have them automatically create a new "case" (or task list for this purpose) or get appended to an existing case.  When people ask me to do something, I usually try to get them to email me about it rather than just mentioning it off the cuff in the hallway or whatever, and that way, I can just forward their request right into FogBugz as well.

Basically, the workflow you described in #2 is exactly what FogBugz does in a more automatic and easier to organize way.  I really like being able to have a chronological list of "notes to self" on a particular task, because I often find myself thinking about something I have to do even when I don't really have time right then to work on it, and whenever I have an idea that I don't want to forget, I can easily update the "case" in FogBugz and go back later to jog my memory.

I can't really give you any feedback on how hard it would be to implement the language features that you need, but I did actually end up "hacking" a few things here and there that bothered me, and as you said, it was really pretty easy to do because other than the email service, the whole product is just an ASP web site.  In fact, the code behind it is really very simple.  What you're really paying for is the thought that went into designing the workflow of the product, I suppose.

At the time we bought FogBugz, Joel was offering a free online trial where you run the product on their server instead of your own.  I don't know if they are still doing that or not, but if they are, you might want to try emailing Joel if you haven't already and see if he'd be willing to let you also test localization that way.  I don't know if I've just happened to catch him when he wasn't that busy, but Joel has always been very responsive to my email requests about his products...