I disagree with a problem with an extra package: this is such a
low-level detail that average users don't need to really be aware of
the existence of the package, and I think the marginal increase in
compile times shouldn't cause any issues. I used to worry much more
about adding extra packages to the mix, but with the more recent
versions of cabal-install and the community's general improvement in
handling dependency hell, I see less of a reason to do so.

I only mention this because one of the Tsuru guys mentioned to me that they stopped using Snap because it had too many dependencies -- they're not using Cabal internally. Of course, Yesod is even more of a non-starter for them because of this issue.