I strongly suggest doing some tests with the following cases:

A) More than 10,000 pages of data!

B) A couple indexes, to watch behavior differences when SELECT, INSERT, UPDATE, and DELETE happens

B1) An index on a field whose INSERTs and UPDATEs tend to be sequential (say, current date/time)

B2) An index on a field whose INSERTs and UPDATEs tend to be arbitrary (say, date of birth, though SSN is an even better example

C) A third fillfactor example; between 85 and 95

D) Extra credit: Unique and non-unique

One not uncommon case for indexes in many systems is:

Millions of rows

Index on SSN-like field

DML operations are effectively on random SSN's, usually one at a time

Single row SELECTs on the SSN-like field are common

Bulk data SELECTs are perhaps uncommon, but certainly not rare (select SSN, col1, col2 order by SSN-like field)

Very, very quickly you'll find that a fillfactor in the high 90's results in a much smaller index than 100 would; likewise, it needs to be rebuilt/reorganized less often (also important if one has a small maintenance window).