quilt

MichaelBanck: "The new kid on the patch system block. Very successful for difficult packages like glibc, X.org"

?HendrikSattler: quilt is much more intuitive to use. Using dpatch is a science for itself.

dpatch

Widely used, integrated with e.g. cdbs, but considered inferior by some because of crap merging support.

?FrankK├╝ster: dpatch as an example for both success and non-success: It's great for many applications, but for large source trees other tools, like quilt, are superior.

madduck: dpatch & co seem to be more accessible: they are files you can "touch"; they're not an abstract concept ("branch") which you can work with, but which is not tangible.

dbs

MichaelBanck: "Probably a winner at its time, but these days, superior systems for all of dbs' applications exist and only very few(?) packages still use it"