Its mostly all true, but all of the problems were fixed. There is no linux distro that is released without bugs, and since Mandrake has so many features that distros like slackware don't have, it is more bug prone.
If I remember correctly, Mandrake isn't the only distro to use a pre release kernel. Red Hat and Fedora both did this too. Also Suse had a broken gui utility a while back too.
Mandrake is an overall great distro, and has no more flaws than similar distros and the flaws are fixed quickly.