We've been talking about this since November...but newbies may appreciate seeing it front-and-center again.
As for copying files, connect BB to your PC using USB cable, enable mass storage mode when the prompt appears on the BB, and copy to the card via Windows Explorer. Very simple.
It's USB 1.x, so the speed of copy isn't impressive.
If you have a micro-SD card adapter, copying directly to the card is much, much, faster.
I've had my 8GB card since November, no issues w/the hardware, it has about 1 GB free...got music, pics, and movies on it.
One thing you may run into is "disappearing" audio tracks or movies. Has happened to me a couple of times, always after I have just copied or rearranged files on my SD card. The only way that fixes it for me is to remove the offending diretory, and copy it and contents back to the card. Someone posted that deleting the DAT files that the BB creates in the folders helped, but that didn't do anything for me.