I've played for 45-ish hours, and I've gotten slowdown, choppiness, 90+ second load times, enemies clipping into rocks, followers disappearing forever, and of course the occasional full-on crash (freeze, no guide button, requires restarting etc.). Though I have two favorite glitches so far:
The first was when I was out in Primm when I found and fixed ED-E. I had Rex with me, so I sent him back to the Lucky 38. Later on I wanted to continue Rex's sidequest, but he was nowhere to be found. I thought I was screwed, until I found him sitting in the King's hideout. Before I could even walk up to him and ask WTF, he all of a sudden ran towards the door and left. When I chased after him, he magically disappeared, and I found him again in the Presidential Suite.
The best glitch by far happened during an assassination quest (I won't say which one, but you know what I mean). When I sniped my target, instead of dying or exploding, he floated up into the sky like he was on an invisible elevator. When he got like 200 feet in the air, he fell back down to the ground and died on impact.