We have replaced a few 8x 15K RPM RAID5 with OCZ PCI cards of 0.5TB and 1TB. They were serving databases with high update frequency (~500Hz average in the long run). At first they were fantastic, iowait was gone, great performance, just as expected, enough to get us hooked on them and order more :)
However in a few months the performance has deteriorated dramatically, to the point where they were much worse than the disks they were replacing. Writing /dev/zero to them a few times restored for a short time the performance but finally one card died dramatically, another lost 2 of the 8 slots ... Finally we moved back to the disks and as much RAM as fitted the servers and called it a failed, very costly, experiment. I'd argue that the SSDs are probably good only for PCs since one can fit a comparable amount of memory in a server for read performance and if you need high write rates you would anyway destroy them quickly...