Many filters are designed/needed for film, few are useful for digital. IMO, the useful ones (i.e. effects cannot easily be replicated in post) are
+1 ... I've got clear b+w protection filters on my lenses with no iq drawbacks - some lenses even require a filter for full sealing. I'd like to add that polarizers mostly don't work with wide-angle due to too different angles towards the sun. I thought grad filters are analog old-school, but after what briansquibb wrote maybe I should think again? How often do you use them (for static scenes I'd just do hdr or exposure fusion, that's when IS comes in handy, too)?
It's a pity polarizers & nd are so expensive for 82mm - but I guess if I get the Tamron 24-70, there's no way around it. Shooting water/glass with a polarizer is extremely useful, and bulb with nd is great too.