I installed a 480GB Ultra II SSD today on my mid-2012 Mac Book Pro. It’s running Yosemite with Trim disabled. BlackMagic and Disk Sensei show read speeds in line with the SanDisk quoted at 542MB/s. Write speed seems lacking somewhat at 214MB/s. The SATA link speed is 6GB/s, as is the Negotiated link speed. The SSD is installed into the HDD bay.
The disc is only 30% full and the drive was only installed today so I don’t think the lack of Trim is an issue.
Anyone got any ideas why the write speed should be so low?