I've installed probably 50-60 glass screen protectors over the past 5 years (using bathroom steam process) and typically it takes 2-3 tries to get a pristine install (I have real OCD). The X is far worse because the notch makes any otherwise unnoticeable misalignment painfully obvious (rainbow effect).
I tried 4 of the best protectors on delivery day and even using the install alignment tools, it was never "perfect". Went to the Apple Store and had them install a Belkin. Before he gave it back to me, I noticed a small dust spot so had him do another. That had a chipped edge so had him try again. The third one was perfect and has been for the past week I've had it. Smoother than most, soft edges, and no issues thus far.