I am using a Crucial M4 SSD 128GB for OS and apps in my Mac Pro. So far, so good. BUT: All the data is on internal HDDs. Using the first HDD for frequently or even daily used data, the second HDD for not often used or older data and the third one as internal backup for the SSD and the two other HDDs. Of course having another external backup. Starting the apps is of course great most of the time. But I have a problem with the access time for data. Why? Because the internal HDDs are often sleeping while beeing in the internet or doing mail stuff. And it takes a lot of time (a couple of seconds) to awake them and get the data available. Should I put the frequently used data on the SSD also to avoid that or is there another maybe better way?! How do you guys handle that? Saw the apple event yesterday and the announcement of the new iMac with Fusion Drive. It sounds like Mountain Lion is putting most needed data on the SSD by itself and back to the HDD when not used for a longer time. Nice. Should therefore be possible with Mountain Lion in general. But I guess Apple will handle it the same way, as they did it with TRIM for different SSDs. Probably not available/realizable. Too bad.