Installing Non-Debian Programs w/out Apt -- what effect?

[Hal Vaughan <hal@thresholddigital.com>]

Now that I finally have a working Debian system, I want to know what will 
happen if I install non-Debian programs.  I know this will vary from case to 
case, but I'm wondering what the general impact is if I have to install 
programs that I can't do from apt.

For example, Main Concept will be coming out with a pretty good video editor 
soon (Main Actor), and it'll have its own install program.  I'll also need 
Open Office.  (I know there's a package in Sid, but this is for production 
boxen for my company -- I don't have time to deal w/ unstable and fix things 
as they break -- I'd also like to try to keep my system as stable.)  If I 
install programs, do they generally not interfere w/ apt?

And, while I'm on it -- once a program is packaged (like Open Office) and is 
in unstable, is there any general rule of thumb for how long it takes to go 
to testing and finally to stable?

Hal