the stability thing is probably kernel, go back to an older version, or better get involved in kernel development.
to get your system to boot faster,
- remove unwanted servies (with YAST's runlevel editor or better by hand removing stff in /etc/init.d - the bootscripts and the files that are called Snnservice in your favourite runlevel)
- stop using KDE, try gnome, or for lightspeed use MWM as your windowmanager, also use xdm not kdm as the display manager. if you love kde get a version that is 5 years old that hasn't got so many features(bloat) or turn off the cute visual effects
- if you have time to experiment, recompile the souces of all the programs you ever use like bash, X, the KDE suite, everything in /sbin etc... for your CPU using the --target (and probably --force) option in rpm but you only get about 50% for a lot of work
- complain to suse