I bought a couple of WL4000GSA6472E drives recently (currently $130), but I ordered them separately a couple weeks apart. It looks like they're mixing different models since I got two two that differ a lot in firmware and benchmarks (using HD Tune Pro on same system and SATA port). They look the same externally though.
The first one was ordered on 2/23. Firmware HPG1; read transfer rate average 136.8 MB/s, max 170.6 MB/s; random access read 512kb @ 79 IOPS, average access time 12.6ms.
The second one was ordered 3/2. Firmware 01.01A01; read transfer rate average 124.6 MB/s, max 143.5 MB/s; random access read 512kb @ 60 IOPS, average access time 16.5 ms.
I don't have any WD enterprise drives to compare to, so all I know is that the second is different and a lot slower - particularly in random access. I have more drives on order, so hopefully I get more of the former than the latter.