1) does it force the use of RPM? Some prefer DEB, or even ebuilds.
Yes, because it produces a openSUSE derivative.
Fortunately, openSUSE also comes with zypper as high level tool. It's quite like apt is a high level tool to dpkg and DEB packages.
For a comparison:
- rpm -i <-> dpkg -i
- zypper install <-> apt-get install
Zypper is also just as fast as apt-get. So it may not be that bad after all. :-)
Secondly the openSUSE build service allows you to search for an insane number of packages in community / addon repositories.