We really like PCMark 7's Secondary Storage benchmark module for its pseudo real-world application measurement approach to testing. PCMark 7 offers a trace-based measurement of system response times under various scripted workloads of traditional client / desktop system operation. From simple application start-up performance, to data streaming from a drive in a game engine, and video editing with Windows Movie Maker, we feel more comfortable that these tests reasonably illustrate the performance profile of SSDs in an end-user / consumer PC usage model, more so than a purely synthetic transfer test.
Though the Crucial M550 series drives finished at the bottom in terms of overall PCMarks, keep in mind there is only a roughly 2.2% delta separating the "fastest" and "slowest" drives here. If you look at the individual scores, the M550's actually offered class-leading performance in the starting applications test, the deltas separating the drives in the remaining tests are quite small.