I found something I thought was quite cool today, having multiple swap partitions on Linux with the same priority causes them to be used in a round-robin fashion, similar to (I should imagine) using a RAID striped partition. From man swapon(2):
“If two or more areas have the same priority, and it is the highest priority available, pages are allocated on a round-robin basis between them.”
So, exlicitely setting setting the pri option for multiple swap partitions on different devices in /etc/fstab should give some performance improvements for paging in and out. I did try to benchmark it, but didn't find a good tool for it.