Running a mixed system

[Wu-Kung Sun]

With the major changes in sid I'd like to know if running a mixed stable/unstable system is ok.  I'm working iwth an install of sarge when it was frozen just before going stable but I've got apt pinned to unstable. I don't normally install much but lately trying to install latex and firefox 1.0.7 aptitude wants to restart kdm.  I've made a mess doing lesser things so I'd like some feedback.  If I go ahead with the install will my system be borked?

Also, has seamonkey been debianized yet?  If so what is the package name?
Thanks!

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swk