Los Angeles, California, US
I have the Epson V750 and use Silverfast and am quite happy with it. I do not recommend the 35mm holders that come with the scanner. For 35mm i use a dedicated 35mm scanner. For 120 the Epson works fine with the stock holders as long as your film is flat.
I use vuescan with the Nikon 9000 . If you are going to post edit your scan with PS or LR then vuescan is all you need or should use. Ideally you should just be scanning for a digital negative to be tweaked later.
I have been using VueScan for long time and I have nothing but good things. With VueScan, when you purchase a license and bought new scanning devices, you can use VUESCAN with the new device.
Unless SilverFast changed things around since I last read about the product, you buy a licence for the specific product.
For example, I have the not defunct KonicaMinolta DiMAGEScan Elite 5400II. With SilverFast, I could only use the the product with my scanner. What if I decided to buy (for example) the Nikon CoolScan? I'd have to buy another version of SilverFast.