I had one similar problem with my OnGuard Mini the day after I got it. I'm used to the insert-and-twist simultaneous motion that works so well on Kryptonites. I tried that on my OnGuard and found myself about 3/8 the way around with only half the key in. It took a little wiggling to get it properly position to get the key out. Since then I've been careful to fully insert the key before turning. I believe a shop owner posted a similar warning on the Krypto thread. Lesson learned.

Still, I would rather that sort of sucking (the kind where the onus is on me to not screw up and it's pretty easy to avoid) than the other (the lock mechanism is fundamentally flawed and there's no reasonable way to secure it).