I installed this product along with a 480GB Mercury Extreme Pro 6G 2.5-inch 7mm SATA 6.0Gb/s Solid-State Drive (the Data Doubler pack from MacSales) using the instructional video provided by MacSales. Took no longer than 15 mins and was as easy as pie.
However, on testing the new installation on my mid 2011 27" iMac, the drive speed was not that much faster (from 160 MBPS HDD to 250 MBPS SSD) which, after some research turned out to be due to the optical drive SATA port being a 3Gbps port and not a 6Gbps port. After a little more investigating I found that there is a spare 6Gbps port on the mid 2011 model which is empty.
So I reopened the machine and successfully moved the connector to the spare port on the logic board (using one of the mac sales tutorials) and its working perfectly now. By doing this, Read speeds have been bumped from 250 MBPS on the 3Gbps port to 380 MBPS and write from 250MBPS from the 3Gbps port to 500MBPS.
I would suggest that macsales put a note up on the website or add an annotation in one of your videos for others to see as this is a key piece of information for people purchasing the data doubler to replace their optical drives on 2011 27" imacs.
In summary - keeping the above mentioned info in mind, the data doubler should not take more than 30 mins to install. This was the first time I had ever opened a mac so if I can do it - so can you! Just be very careful with the logic board connectors and don't try to rush anything.
In any case - Thank you MacSales for providing such a fantastic service, quick international shipping and excellent support. Well done.