It is the same as Kodak D-76, which has been a benchmark for developing film forever. It is the developer most often used by the manufacturers to test films, and gives a good balance of speed, grain and sharpness.

See Ilford's publication on FP4+ and recommended developers for best overall image quality:

http://www.ilfordphoto.com/Webfiles/...2125850702.pdf

And here is an additional publication from Ilford with broad comparisons of developer characteristics (see page 3):

http://www.ilfordphoto.com/Webfiles/201142713062331.pdf