from testing to unstable
 

Testing 2.6.15
Hi ,
Just to be sure , Is it really that simple to go from testing to unstable and vise verse , just to change repository ?
Would there be side effects when getting back to testing ?
Thanks.

I had no problem to do testing->unstable, but it highly depends on the day you do it, for example today, python2.3 fails to install (it took me 5minutes to find a workaround by looking at bugs.debian.org).

I have not yet tried the opposite way, but this may help you:
http://linuxmafia.com/faq/Debian/downgrade.html
(i hope its not outdated..)