The Samsung 840 EVO is a game changer. The reason why is because Samsung let go of marketing and benchmark performance and shifted their focus to real-world user experience in a consumer environment. Even though the maximum performance in benchmark numbers increased, the minimum and average performance went up significantly in the daily use programs. When we write data to our SSDs, it's not in long sequential runs, except when transferring files. By caching everything going to the drive, the operation takes less time, and thus it feels like the drive is twice as fast as the previous generation.
I'm writing this review right now on a Lenovo T61p with an 840 EVO 750GB with RAPID Mode enabled. This notebook uses SATA 1.5 and it feels as fast as my Haswell system running 16 840 Pro 256GB drives on an Areca controller with a 4GB cache. That's the same system we just broke the PCMark World Record with a week ago. I've said it for several years now, perceived performance is more important than benchmark performance. Anyone that purchases the 840 EVO 250GB or larger capacity size will understand firsthand what that means.
That said, there are some drawbacks to running a system with 1GB of cache. If Samsung uses the cache for a 50 / 50 split, half for writing data to the SSD and half for replaying the data, then you can have up to 500MB of data sitting in the DRAM at any time that is not on the SSD. I suspect the cache is dynamic and if that's the case, then the data waiting to go to the SSD could be even higher. Paul, our enterprise SSD reviewer, would freak out and if a system is unstable, he would have cause for concern. If you are overclocking your system and running on the edge, RAPID Mode isn't for you at all.
The 840 EVO also brings with it a handful of hardware features that are new to the Samsung SSD brand. Full Disk Encryption has been a hot topic for 2013 with announcements from LSI SandForce, Micron / Crucial and now Samsung. TCG Opal and eDRIVE support with the 840 EVO is an important topic for our notebook readers.
In the 250GB capacity size, Samsung hit the market with the 840 EVO. Sitting between the 840 and the 840 PRO on paper, I think the 840 EVO is a superior product to both as long as the P/E cycles hold up. At the conference in Korea, Samsung stated they are achieving higher than 2,500 P/E cycles with this flash, but their testing is ongoing. I wouldn't download my Usenet content to the drive, but for an OS / programs drive, I wouldn't be worried too much.