We have had SimplyMap at Multnomah County Library for several years. I think the biggest users among our patrons are small business people who are building business plans or who need marketing data. And of course, business school students from our local colleges & universities use it too (I don't believe any of the nearby academic libraries have it). I agree that the easy access to census data is great, but some of the other data sets are pretty wonderful too.
Patrons who are new to this kind of research often find the database intimidating -- it's a little complex for the novice -- but the help videos are fantastic, and I generally find that once I show a patron the ropes, they can use it on their own fairly easily.
I'm not responsible for dealing with the vendor, but my sense from talking with our electronic resources librarian is that they're pretty great to work with. They've come to do workshops for our staff a few times, when they have recently added new data sets or had interface upgrades.
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Emily-Jane Dawson | reference librarian
Multnomah County Library
"There is no such thing as a moral or an immoral book. Books are well written, or badly written. That is all."
– Oscar Wilde, author's preface, The Picture of Dorian Gray