SUSE's OBS is in my biased opinion (I work at SUSE), probably one of the better ways of solving this problem for ISVs. You don't need a build infrastructure, you can get feedback from distribution maintainers and submission to the main distribution is surprisingly painless. Actually you can build packages for non-SUSE distributions on OBS as well, so it's even more versatile than just the openSUSE community's distributions.
