The scanner is surprisingly good with negatives. They've turned out well so far. The default color correction is good if a bit high in contrast, and color sync tends to make the images a bit blue. Naturally, the scanner has ICE and all the other fixer-upper technologies for dealing with scratches and color fixing, plus you can adjust color manually by histogram (level), curves or sliders. The software is TWAIN compliant, though there a rough patch for a time where the software wasn't playing nice with Image Capture. My complaints about it are with the software UI -- looks bad (half-ass Aqua) and is sluggish to react, the preview window has some quirks, and the auot-crop feature is a bit too aggressive. Most of the software outside of the actual scanner app are worthless IMO. I don't know if they're all bad, but I just don't use them. Still, though the UI isn't so hot, it's usable, and once you figure out a workflow, you don't have to worry too much about it.
The 3170 comes with 3 film/slide holders. They're pretty low-tech, but actually I think that's a good thing, less to break or. You just place these things on the flatbed in one corner, and either slide in the film strips or droip the slides into the holes for them.
here is the film negative holder, as an example (image from a replacement parts company). There's one holder for medium-format film (one exposure at a time), one for slides (4 slides at a time) and one for film negative strips -- 10 frames at a time IIRC. Oh, and it can scan multiple items, either prints or negatives, at a time and save them as separate files.
OK,
here is a page at Epson with a bunch of .pdfs about the scanner and info on the film holders.