Dear Dover, "direct drive"? You hear speed instability in a direct drive turntable? All of them or one or two samples? A truly vintage direct drive turntable that has not been serviced can manifest speed instability due to aging capacitors, but the technology is not in any way speed unstable per se. If you hear speed instability in a direct drive turntable or if speed is grossly unstable by observation of the typical built-in strobe, then the table is defective.
I am not qualified really to hold forth on belt creep. Instead I can recommend that you go to Vinyl Asylum and do a search on that term. Then read the relevant posts by Mark Kelly. Belt creep is not incurable, by the way, as Mark shows. But also take a look at the Artemis turntable, where the belt travels around a capstan so as to nearly fully encircle the platter, a la one remedy suggested by Mark and others. But really I did not mean to detract from your pleasure with your turntable or to infer that it cannot be fantastic just because of this theoretical issue. I apologize if you got that message.