Funnily enough another one failed today. About 800 power on hours in a Dell Latitude E5520. Same symptoms as before. System hanging and stuttering and getting BSODs, with iostor.sys storage timeouts in the event log. Run a SMART test and it might pass a quick test, but it'll fail a long one with bad sectors. Copying the data off the disc reports bad sectors that have to be skipped. Copy performance very slow - 700MB/minute imaging the drive to another disc.
So far every one has been "fixed" by a secure erase followed by a few hours left sitting in a machine powered on and in the BIOS, as advised by Crucial's telephone support, but I cannot possibly re-deploy these drives even if they are no longer displaying symptoms. After this one today I think I'll be pulling the lot out of service as these users are all over the world and cannot afford unplanned downtime. Seen this now on 256GB and 128GB drives. My colleague has a 512GB version of this drive in his personal Mac that he bought with his own money, and as you can imagine now has cold feet!
Crucial's support have been fairly useless, I don't know if I'm alone in facing these issues with these drives but if not it's a pretty big problem. Usage patterns are entirely regular and boring, Windows 7 / Office 2010 use with some CAD viewing and other boring business usage. Not power users by any stretch.
As an addendum - I have loads of Samsung PM800 and PM810 (also known as 470 series) drives supplied as OEM fit in Dell machines, all working very well indeed after a couple of thousand power on hours and some with very heavy use.