And another thing to add here is that HDRI IBL is mainly useful for indoor scenes or scenes involving lots of objects which have reflective surfaces, such as a car and you want reflections off various real life buildings and light sources.  If you are doing a distant lake scene then IMO it is far less usefull. As stated above though, expect very long render times if using higher quality settings - particularly if you are using glass objects.

Have a look at recent Bryce 6 renders in the galleries. Often they will state if HDRI has been used.