Attached Link: Olympus E500 write speeds

For your info, attached is a link to E500 write speeds to different cards.

Also for your info, with the higher speed cards now available...the limit for most cams is no longer the card itself....but the cams ability to write.  Most DSLR's only have the ability to write from the buffer to the card at 8 to 10MB/sec...the newer cards could accept faster write speeds...if the cam could keep up.

In other words....you would likely see no improvement in going to the Extreme IV in your case.

Other than emptying your buffer quicker, these high speed cards offer two other benefits;

1. Less time writing to your card preserves battery life
2. High speed cards allow you to download your images to your PC much faster.

In youth, we learn....with age, we understand.