Are you talking about the Kiln servers, or issues with client software? The servers are hosted, so you don't need to worry about any requirements or cross platform issues.
I hope a "firewall" install returns as an option someday, at which point we would eagerly reevaluate our choice...
It's quite sad as our company specifically can't hold source code and other information in an external environment (especially across borders) due to the nature of our client base.
Disclaimer: I work for Atlassian on Stash