I realise this thread is a bit old but I am new here and wanted to add my thoughts.
I shoot almost exclusively Velvia in large format - 4x5. It is a wonderful film for seascapes and waterfalls expecially.
I rate it at 50. I know some others like to rate it at 32 to try to bring up some more shadow detail but I find it is very sensitive to over exposure (as are most slide films). It only has around 5 and a bit stops of range so you need to meter very carefully. I suspect 32 might work for exposures under a second or so. Most of my exposures are more like 8 to 10 seconds.
As others have mentioned - you can get a magenta cast from expired film if it has not been stored properly. And occassionaly some green from very long exposures.
There are 2 variations of Velvia. The RVP100F is a nice film but does not have the same vibrant contrasty saturation of the old formula RVP-50. The 50 was discontinued some time ago but Fuji re-introduced it a while back. I use both but much prefer the 50. The 50 is harder to get and more expensive because most landscape photographers love it.
I also process it myself at home with Tetenal's 3 Bath E6 kit. Does a great job. And is a lot cheaper than the $10 a sheet I get charged at a lab!
As nightbringer says - Velvia - why I shoot film.