if this is the new 2.3 version - there are quite a few people running custom roms who can't install it (installation unsuccessful)
just a heads up
Yup... well actually is just depends on what Gmail version you are running. If you are running 2.2.1 you most likely will get the error. Reason being is that that apk had to be patch to work with the voice search.
I know Virtuous 2.7 dev rmk40 expected this issue.