[glandium]

I, personally, believe it's up to a user to decide which version control system works best for them.

Both git and mercurial can talk to "non-native" remote servers.

IIRC mercurial can talk to subversion and git (with hg-git).

Git can talk to subversion, cvs, perforce, mercurial (there are multiple tools for the latter, and I'm the author of one of them), bzr, and maybe others.

If things don't work smoothly in any of those cross-VCS configurations, my belief is that issues should be filed and fixed.

[dmitry-k]

Agree. However, large enterprises usually have common compliance/access control policies, something not easily implemented across multiple VCS (unless there's a full-fledged internal development team dedicated to that).

Working in a big firm adds overhead, yet has certain benefits (resources, etc.). That's a whole different topic though.