I have the 240gb version and so far it seems fast, reliable and on par with similiar current gen SSDs. The Intel SSD Toolbox software is also a nice feature, gives you all the info you need on the drive (health check etc), has error checking facility, TRIM optimisation (which can be schedueled) and a tool which checks and changes windows settings for best performance with SSDs.
That said, I think they are currently overpriced. Yes you get intel reliability, but other manufacturers are on a similiar level now and can offer better peformance too.