I got my pair in yesterday. I have some quick benches using CrystalDiskMark for a single drive and a Storage Spaces' RAID0 across both:
Single Drive
Read Seq - 490.4 MB/s
Write Seq - 452.3 MB/s
Read 512k - 337.9 MB/s
Write 512k - 423.9 MB/s
Read 4k - 22.25 MB/s
Write 4k - 45.61 MB/s
Read 4k QD32 - 326.2 MB/s
Write 4k QD32 - 345.9 MB/s
SS RAID0
Read Seq - 913.9 MB/s
Write Seq - 870.0 MB/s
Read 512k - 536.9 MB/s
Write 512k - 795.9 MB/s
Read 4k - 21.71 MB/s
Write 4k - 42.73 MB/s
Read 4k QD32 - 370.9 MB/s
Write 4k QD32 - 385.1 MB/s
ATTO managed to pull over 1GB/s read speed. This was with an i5 2400 and using the standard Intel 6Gb SATA connections on my motherboard; the disks were passed through raw from Hyper-V to a Windows Server 2012 R2 VM. So, these seem like great drives, especially given the price they were purchased for!