The Tech Report have updated their storage testbed to properly benchmark PCIe SSDs, the M.2 versions as well as ones such as Intel's DC P3700 which takes up a full slot.  They contrast the performance with 10 popular SATA drives to give you an idea of the difference performance a PCI SSD will give you.  The rather expensive DC P3700 dominates almost every test they performed, apart from boot times in Windows 8.1 which are still well under 1 minute.  Read through the review with your own usage patterns in mind, in many cases a SATA SSD is still a great choice for many gamers and are much more affordable.  Then again, if you can afford a $2500 SSD, Intel's offering is definitely king.

"SSDs have been bumping up against the limits of the Serial ATA interface for a while, but they don't have to be stuck behind the 6Gbps link. Native PCIe drives with way more bandwidth have made their way onto the market over the past year. We've tackled a trio of them—Plextor's M6e, Samsung's XP941, and Intel's server-grade DC P3700—with a fresh slate of benchmarks to see how the new breed stacks up against the SATA incumbents."

Here are some more Storage reviews from around the web:

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