I haven't had the CanoScan Toolbox working for a loooong time with my 9950F scanner. But I've been using Preview and Image Capture just fine on my iMac with Lion 10.7. (Wish I had stayed with 10.6!) Don't know why people haven't been able to run Lion with the 9950F. However, I've just 'upgraded' to Mountain Lion 10.8. Thought it was kind of a tweak except for IOS junk thrown in. But, I was wrong, and now the scanner doesn't work.
However, I've been running Quicken with VMWare Fusion with a very old version of XP and thought I'd give XP a try at downloading the XP version of the driver and toolbox. Works pretty well if you're patient for stuff under the covers to do whatever, and after a while the scanner starts up. I now can use the XP version of CanoScan Toolbox for Copy, PDFs, and Save! If you want to scan stuff into an XP folder, you can then just drag the file and dump it in DropBox, Evernote or whatever OSX folder you want.
I also tried sharing the scanner attached to my iMac on the network to my MacBook (white) which can't be upgraded to 10.8 and is stuck at Lion (I REALLY wish I had left it at SL). Then with Preview or Image Capture it looks like it tries to work from the MacBook, but I can't get that to work. Maybe it takes a working host, but it's beyond my limited expertise!