Jim and I work together and he pointed me to this post. Thought I might have a few comments to make here.
I have used all three systems Jim mentioned.
I really like Xtra reports. The designer is excellent and has a lot of neat features. From the time I installed the demo to the time I actually ran and tested my first report was in the neighborhood of 2.5 hours, which I found very impressive. It was not a terribly complicated report, but was a good challenge for a first time use with groupings and summaries along with the detail. I used GenPro objects directly and bound to them (using normal Databind methods! Even though they are Xtra reports own homegrown version of the method). In particular, I'm using Xtra reports on a web project and it was beyond simple to send a PDF back to the client. They actually have a method that converts the data to and properly encodes for the http response and everything - you just call that method and don't worry about anything. I recommend Xtra Reports heartily.
Active Reports isn't bad. It has some flakiness in its designer. The last version I used was unable to set the data source to anything other than an SQL statement, although now I understand that it will accept standard object binding in its latest release, which I have not upgraded to. You can't derive objects from the base reports (as of the version I was using) which was due in large part to the flakiness of its designer, from what their tech support folk told us. I was also unable to ever find a way to set the data source for a subreport in the actual report, which I have a real problem with. I had to set the data source in the parent object's class. When I tried to put it in the subreport I got no data. ActiveReport's own examples showed putting the assignment of data source into the parent report and when I did that everything worked fine. If they fixed some or all of these things in their latest release, I'd say it's a real contender.
What I have to say about SQL Reporting Services is all related to SQL Server 2000 and working with it through VisualStudio 2003. I wouldn't touch it with a 10 foot pole. They may have improved it in the latest version of SQL Server and Visual Studio, but I have not tried it yet (and probably never will). I found the designer to be fairly useful - until I started hitting all the bugs. Simple things like going in and changing the sql statement doesn't mark the editor as dirty and if you're used to closing a form and having it prompt you to save, you're SOL (this is not the case when the editor is in "New" mode, only subsequent edits, or on "dirty"). You can't change datasources on a report without changing that report for every user, as it always hits the version of the report stored in SQL Server (i.e., you're not instantiating an object but making a request of a static report definition in a database). Pointing a report to a different database was not too difficult using parameters passed in through the web service call, but forget about changing servers (there are ways to handle that kind of stuff - but you have to code your own data source [which is far from easy] and still pass in those parameters)! And last I knew, there was no way to use the built-in functionality to get headers to print on every page when a section (I think it was the List control, if I remember right - there was a flag to set it to do just that, but RS ignored it) crossed pages - it was a known bug that MS said was not going to be fixed in that version (SQL Server 2000). There were work-arounds to get that functionality, but it was a pain. Unless you need a lot of the other functionality it offers, like automatically delivered reports via email (which can be done almost as easily writing your own service anyway), I don't recommend SQL Reporting Services unless subsequent versions are substantially different and fix these issues. Any of the other products can easily create all the formats RS does.
Now, this was mostly in response to Jeff's question, as I have never actually created a PDF form before, which I imagine is a whole other topic for discussion