We have emacs and xemacs, if that weak analogy helps...
I don't think "experimental" is necessary, the package system isn't at risk. From a user perspective, I guess I'd like to be able to have both installed so that if one doesn't work for something I could try the other; likewise for hacking on dsssl-style sheets, it would be nice to test them against both before release... so that's an argument for having them both installable together, if it isn't too complex...
