Sounds like a good idea - I'll have my S95 with me.
Especially the histogram might help a lot to see the scenes luminosity distribution in a more technical way.
Since you have a Canon this opens up yet another option. You can load the Canon Hack
software onto a memory card which then enables all sorts of options such as a live RGB histogram, clipping indicators, Zebra mode which highlights all the blown and blocked up parts of a scene, and various other fun things.
Velvia was the trickiest film I ever used. The only way I could be sure of getting an optimum exposure was to bracket.
But it gets worse, what looked to be the optimum exposure on the lightbox was often not the optimum exposure for scanning. And it gets even worse, the optimum exposure for scanning depended on the type of scanner. Flatbed scans couldn't extract anything like the shadow detail of drumscans.
Boy did I find out about that one the hard way. After my initial struggles I finally managed to get pictures which looked great on my slide projector only to have them look like complete crap when I tried to scan them. Then again I have a cheap consumer level scanner which is only used for sharing photos on the web, when I had the same pictures scanned by someone using a Nikon 9000ED the results were a lot better but it still flaked out on a few pictures. I've considered having one of those frames drum scanned just to see how it turns out but haven't gotten around to it yet.