Apple's new Compressor v4 allows you to control bitrate for MPEG-2 elementary streams (i.e. for DVD disc creation). It also offers Dolby digital audio. Thus, if you're mainly interested in compression for DVDs then Apple's Compressor application at only $50 is a pretty good deal.
However, it really doesn't offer much in the area of DVD authoring (i.e. custom menus and navigation). You can create a basic DVD with a title screen and chapter selection but that is about all it can do as far as burning a finished disc (as far as I can tell, but I haven't researched it extensively, there may be more support for custom disc creation than I know about). You can download the Compressor v4 User Manual from Apple's website it you want to see what it can do.