My experience so far -
Lexar 1000x 32GB - Red rings frequently with preview.jpg error, no longer use
SanDisk Extreme 32GB - Only had one Red ring with entire image corruption, believe this was the unit overheating and not the card
I like the SanDisk since they also work well in GoPros, they seem to work fine in the iris, and fast transfers. Get extra cards, if for some reason you do get the red ring you can normally just switch off pop a new card in and get right back to work.