I just ordered one of these drives from newegg(250GB for $187)I've seen them sell for more and less, they are really nice from what reviews I've read. And they come with a proprietary software called RAPID that uses 1-2TB of system RAM for caching, and while it has some bugs to work out, in most cases transfer speeds went from 500~MB/sec to over 1,000.
A closer look at RAPID DRAM caching on the Samsung 840 EVO SSD - The Tech Report - Page 1
they are available in 128,250,500 and 1TB. Here's a review of all of them. Which gives some history to SSD's and the 840 line.
AnandTech | Samsung SSD 840 EVO Review: 120GB, 250GB, 500GB, 750GB & 1TB Models Tested