JSTOR is brilliant because it is a keyword-searchable collection of major databases.
The problem with JSTOR is that it lacks metadata or meaningful indexing, so it's limited to keyword searches only.
EXAMPLE
If I'm interested in women's education in Virginia during the 19th century, I'd use the search
women AND virginia AND (Education OR schools) AND 19th
As you see, JSTOR gives me tons of results because it's keyword searching the entire article/record for those terms.
Conversely, a specialized databases like America: History & Life narrows the results just to history journals. It also uses metadata fields to provide more focused searches. Compare to the results for the exact same search in A:H&L
The only time you may want to use JSTOR is if you're looking for something very specific, like the name of an under-studied individual or idea -- someone who may be mentioned in an article but isn't well-studied enough to be the topic of an article (ex. Professor Harvey B. Lane of Wesleyan University).
Please note that I'm working with Library IT to fix this issue, hopefully we'll have a solution soon. Thanks!