I have 2 SATA drives using onboard RAID 1. I heard they are hotswapable as long as they are using the SATA power connectors. Anyone know if this is true?

yes, it's true. You can even hot swap IDE drives in a RAID 1 mirror, you just need the right hardware. As long as the RAID card supports it and you have a hot swap chassis for your HD's it will work.

I recall plugging a IDE drive's power in caused some sparks...you sure you can hot swap IDE?

It is best to purchase a mobile rack to hot swap the drive