Vim patch 7.0.88 rewrote the regexp engine. Unfortunately the new
implementation was causing long delays of 10 seconds or more when opening or
scrolling any file of a type for which vim does color syntax highlighting.
Patch 7.3.1110 attempted to fix this, and more patches released today
correct other bugs in this new regexp engine (including patch 7.3.1111 which
doesn't even fully apply correctly). Even with all the fixes applied, the
new engine is grossly inefficient when compared with the old one, and it is
obvious that vim is running much more slowly even on my fastest machine.
It seems like the best course of action is to take all the patches before
the one that changed the regexp engine and then give upstream some time to
figure this all out. Thanks to Benjamin Trigona-Harany for the bug report.