I had the same issue as stated with the battery cover.
Took it to an apple store earlier and got a full refund. I'm stuck with what to do now..I love the design/features/capability of the macbook but I don't want to be everlasting taking it back to the store.
I was given the option to swap it over, change model or get the refund.
I'm tempted to wait for the Air to come out next month, or just go and get another 2.4!! - It's only for Uni work (MS Office mainly)
I'm stuck!
NB - It's not something anyone should have to put up with when paying £1,000 for a computer, the gap in mine was large enough not only to cause a nuisance with clicking, but also dust/dirt and moisture can quite easily get in to the battery/hard drive compartment..causing much more serious problems.
I exchanged my MB yesterday for a MBP and I'm glad I did. The display (I lucked out and got the 9C84) difference itself was worth the exchange.