I'm going to write primarily about my main card, but most of this also applies to my others (I'll list the brands for those at the end
).
Card:
Verbatim Premium HD Video SDHC, Class 6, 32GB
Formatted as: ext2
Formatted with: KMFormat (a KDE front-end which simply calls the usual command-line tools), under Kubuntu 8.04.
Working fine since: June 3rd, when I received my first Pandora unit. Still working fine.
Problems: None. I did end up with a corrupted psx4pandora file when an early build of that emulator crashed and I had to do a Pandora-button-reset, and I couldn't delete it until I ran fsck, but I would expect issues like that with any file-system due to the application crashing as it did.
Most of my other cards are (or have been) also formatted as ext2, and were formatted in the same way. These cards are an assortment of a couple of 16GB Play.com own-brand Class 4 cards, one 4GB Play.com own-brand Class 4 card, and one Kingston 8GB Class 6 card. I have had no problems with these either, and have also had no problems with my FAT-formatted cards (one of my 16GB Play.com cards is now FAT because I sometimes copy music to it from my Macintosh instead of my main box), which consist of a 16GB Play.com own-brand Class 4 card, a SanDisk 128MB card, and a Kingston 2GB card.
I've had no problems copying between slots with any mixture of these cards, on either of the Pandoras I've had. I will test this again when I receive my replacement unit.
EDIT: Oh, additionally, while I think of it, all of these cards use Grade A flash chips. You can determine this by testing with
H2testw and checking how much space the application says was ok once it gives you the results. If it's a normal amount once you factor in formatting overheads, then it's most likely a Grade A chip. For example, a 2GB card with a Grade A flash chip will give you 1.9GB of usable space, and so on - if H2testw said, say, 1.8GB or 1.7GB, it's probably a lower-quality chip (or one that's gradually wearing down). I wonder if this is worth looking into further?
EDIT 2: I've made my own thread relating to my previous edit
here, because I don't want to cause any derailment in this one.