In case you missed it, Ithaka release a report in September titled "What to Withdraw: Print Collections Management in the Wake of Digitization" [pdf].
It's really geared towards academic libraries looking to achieve a balance between digitizing journals for access (and repurposing the floorspace they took up), and retaining print journals for preservation purposes.
Being a medium-size public library, our journals are mostly for popular reading, but we do keep a small magazine archive of past issues. The criteria I use on which titles are kept in the archive is basically:
Does this magazine contain information that someone will find useful in two years?
In most cases, this includes things like cooking magazines (for recipes), home improvement/craft/sport magazines (for ideas and tips), those useful for research (like Vital Speeches of the Day), and of course, Consumer Reports (we also have a large [donated] collection of National Geographic, dating back to 1911). But the archive has limited space, so it gets weeded every year to make room for new issues/titles.
And no discussion of digitized journals would be complete without me mentioning one of my favorite tools, the Boston Public Library's e-Journals by Title search. I make some journal collection development decisions based on what I know I can access through them, and just hope it stays that way.