NOT FLUSH:
I've noticed - as some others have with their machines - that the side that covers the hard drive is not quite flush with the casing and I wonder if that's to do with how tough that plastic tab is?! Could it be forcing the cover out of place? (Apologies if someone else has already mentioned this.) Anyone without that plastic tab still not have a flush cover?
I just removed my cover for the first time, to put a little padding under the trackpad. Having read about all the issues, I removed the cover VERY gingerly.
I based my approach on the idea that the technician at the Apple store had installed my RAM and the cover had already been removed by them, and yet it fit perfectly and tightly, so there MUST be a method of removal/replacement that facilitates this.
1. At first glance, it would seem that after opening the latch, you have to pull the cover upwards in order for it to come off. Instead, I found that just wiggling it a tiny bit did the trick. My tabs were perfect upon inspection. I have a feeling the tabs are getting bent by people putting too much force on them initially. One thing's for sure though; the removal process is not very intuitive.
2. Upon replacing the cover, I could tell it was going to stick up too high over the hard drive, thus creating an uneven seam upon closing it all the way. Some have probably just tried to push it flat, again, bending the tabs.
I found that there is a tiny bit of lateral (left/right) room when re-seating the cover. It may seem as if you're placing it perfectly, but in reality it needs to move to the right a bit. If you lay the cover in position, tabs first, then move the cover slightly right towards the battery by a millimeter or so, it closes perfectly flush. At least mine did. And if you didn't appy too much force when opening it, you *should* have a perfect fitting, tight battery cover.
Obviously if your cover was loose without ever opening it, this doesn't apply to you.
