"Going hybrid" with Debian versions is not always worthwhile, (or safe, or reliable, etc.), but _sometimes_ it works.
The hybrid version's best case is when a package from _testing_ or _unstable_ makes only trivial changes, (in perpetuity even), and everything works smoothly thereafter. Possibly it's already been packaged in Debian Backports, or some repository or archive like it.
Failing that, provided the package isn't too complex, one can search pkgs.org in hopes of finding something close enough. The **alien** package sometimes helps.
One could go _upstream_ and attempt to compile it, (and package it), but if it's a thorny package this might require more time than one has to spare, (which is why we use precompiled packages in the first place).
The worst case scenario would be a package from _unstable_ that's too needy or quarrelsome, and has too many conflicts with _stable_ , wiping out something _more_ important than the new package.