I have a couple of mdadm raid arrays built on Seagate 5900 RPM drives - when I bought these, they were relatively cheap for the size and offered (some) power and cooling savings over their 7200 RPM counterparts, and offer more than sufficient performance for my needs. I have one array of 8 x 1.5TB drives and another of 8 x 2.0TB drives.

I have moved them from 8 bay to 16 bay enclosures and now have the opportunity to add more volumes to the arrays. (From eSATA enclosure to a SAS enclosure behind an LSI1068E controller.)

These 5900 RPM drives are now hard to find at a price point I want to live with.

Just how ugly will it be if I put 7200 RPM drives in this array?
Anyone have any experience running mdadm RAID 5 on drives with dissimilar spindle speeds?
I'm worried about dissimilar seek and access times causing the RAID to drop drives, but adding new drives one at a time is a lot more appealing that starting over with all new disks....