Another lurking professor here... You ABSOLUTELY have until April 15
to respond to their offer. FSU is a member of the Council of Graduate
Schools, who have all agreed to allow students to consider their
options until April 15. See http://www.cgsnet.org/Default.aspx?tabid=201
for the agreement. The pdf file (link from above page) lists the schools
who have agreed to this resolution.
In terms of how to handle the situation, my advice would be to keep
a civil dialog going with the department. Explain that you are currently
considering several options, among which FSU is highly competitive.
(Politely) remind them that you thought the common reply date was
On a related note, however, for those of you holding multiple offers, it is
very helpful to departments if you can turn down (and, also, accept!)
offers as soon as you have reached a decision. Please don't wait
until midnight on April 15 to turn down 10 different programs! Graduate
admissions is a difficult process from both sides of the application folder --
our concern is to accept and recruit the strongest entering class possible,
but to do so while making certain that we have EXACTLY the number
of students we need to fill research and teaching assistantships. Not
one more, and not one less. The sooner we have firm acceptances or
firm declines, the sooner we can inform students on our waitlist of
their application status.