I think GUI is quite clear, you can show filter and you have select boxes to search for different fields (src, destination, srcchannel, dstchannel, user field, etc,.. also you can search by disposition: answer,busy, etc).
If you think listing 20 field conditions in a huge list is flexible an usable, then you can still use it.. if you think you can improve the builtin issabel cdr, I gave you much more than a pointer on how to work on it. If you want a professional (and commercial) reporting tool, look at http://www.asternic.net for queues and http://www.asternic.net/cdrreports for CDR.
You are welcome to contribute improvements over the cdrreports module.
Best regards,