I've been trying out 14w07a & have had no real problems. A couple little glitches here & there like broken blocks ending up far away or even on other sides of walls. The 1st real glitch I've had just killed me (in the game obviously). I noticed that my mine cart that was off the end of the track when I left off last was now mostly underground. I popped it out & placed it back on the track & rode it back to the station then hopped another mine cart in another direction. Upon reaching the end of the track, I was suddenly under ground & suffocated.